Fair Value Measurements (Tables)
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12 Months Ended | 
Dec. 31, 2016  | 
| Fair Value Disclosures [Abstract] | 
 
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| Assets or Liabilities Recorded at Fair Value | 
Assets or liabilities recorded at fair value in the accompanying consolidated balance sheets as of December 31, 2016 and 2015 are as follows:  
  
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 Fair Value Based on 
Significant Other Observable 
Inputs (Level 2) 
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 December 31, 2016 
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 December 31, 2015 
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 (In thousands) 
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 Assets: 
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 Cash surrender value of life insurance policies (1) 
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 $ 
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 31,475 
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 $ 
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 29,055 
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 Cash flow swaps designated as hedges (1) 
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 2,772 
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 - 
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 Total assets 
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 $ 
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 34,247 
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 $ 
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 29,055 
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 Liabilities: 
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 Cash flow swaps designated as hedges (2) 
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 $ 
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 6,135 
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 $ 
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 9,094 
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 Cash flow swaps not designated as hedges (3) 
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 346 
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 913 
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 Deferred compensation plan (4) 
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 14,824 
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 13,551 
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 Total liabilities 
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 $ 
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 21,305 
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 $ 
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 23,558 
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 (1) 
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 Included in other assets in the accompanying consolidated balance sheets.  
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As of December 31, 2016, approximately $3.7 million and $2.4 million were included in other accrued liabilities and other long-term liabilities, respectively, in the accompanying consolidated balance sheets.  
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 (2) 
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 As of December 31, 2016, approximately $0.3 million was included in other accrued liabilities in the accompanying consolidated balance sheets. As of December 31, 2015, approximately $4.6 million and $4.5 million were included in other accrued liabilities and other long-term liabilities, respectively, in the accompanying consolidated balance sheets. 
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 (3) 
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 As of December 31, 2015, approximately $0.5 million and $0.4 million were included in other accrued liabilities and other long-term liabilities, respectively, in the accompanying consolidated balance sheets. 
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 (4) 
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 Included in other long-term liabilities in the accompanying consolidated balance sheets. 
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| Assets or Liabilities Measured at Fair Value on a Non-Recurring Basis | 
The carrying value of assets or liabilities measured at fair value on a non-recurring basis but not completely adjusted to fair value in the accompanying consolidated balance sheets as of December 31, 2016, are included in the table below. Certain components of long-lived assets held and used have been adjusted to fair value through impairment charges as discussed in Note 4, “Property and Equipment” and Note 5, “Intangible Assets and Goodwill.”   
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 Significant 
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 Unobservable 
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 Total Gains / 
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 Inputs 
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 (Losses) for the 
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 Balance as of 
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 (Level 3) as of 
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 Year Ended 
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 December 31, 2016 
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 December 31, 2016 
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 December 31, 2016 
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 (In thousands) 
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 Long-lived assets held and used (1) 
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 $ 
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 1,010,380 
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 $ 
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 1,010,380 
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 $ 
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 (8,063 
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 ) 
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 Goodwill (2) 
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 $ 
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 472,437 
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 $ 
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 472,437 
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 $ 
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 - 
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 Franchise assets (2) 
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 $ 
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 74,900 
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 $ 
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 74,900 
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 $ 
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 - 
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 (1) 
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 See Notes 1 and 4 for discussion. 
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 (2) 
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 See Notes 1 and 5 for discussion. 
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| Fair Value and Carrying Value of Fixed Rate Long-Term Debt | 
The fair value and carrying value of Sonic’s fixed rate long-term debt were as follows:  
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 December 31, 2016 
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 December 31, 2015 
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 Fair Value 
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 Carrying Value 
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 Fair Value 
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 Carrying Value 
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 (In thousands) 
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 7.0% Notes (1) 
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 $ 
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 211,000 
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 $ 
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 198,871 
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 $ 
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 211,000 
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 $ 
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 198,708 
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 5.0% Notes (1) 
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 $ 
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 284,934 
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 $ 
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 289,273 
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 $ 
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 284,250 
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 $ 
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 300,000 
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 Mortgage Notes (2) 
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 $ 
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 185,979 
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 $ 
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 176,369 
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 $ 
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 174,007 
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 $ 
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 168,410 
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 Other (2) 
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 $ 
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 4,057 
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 $ 
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 4,280 
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 $ 
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 5,192 
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 $ 
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 5,457 
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 (1) 
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 As determined by market quotations as of December 31, 2016 and 2015, respectively (Level 1). 
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 (2) 
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 As determined by discounted cash flows (Level 3). 
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