Annual report pursuant to Section 13 and 15(d)

Employee Benefit Plans - Schedule of Multi-Employer Plans Affecting Period-to-Period Comparability of Contributions (Detail)

v2.4.1.9
Employee Benefit Plans - Schedule of Multi-Employer Plans Affecting Period-to-Period Comparability of Contributions (Detail) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Compensation And Retirement Disclosure [Abstract]      
Pension Fund AI Pension Plan    
EIN/Pension Plan Number 941133245    
Pension Protection Act Zone Status Red Red  
FIP/RP Status Implemented    
Sonic Contributions $ 148us-gaap_MultiemployerPlanPeriodContributions $ 135us-gaap_MultiemployerPlanPeriodContributions $ 120us-gaap_MultiemployerPlanPeriodContributions
Surcharge Imposed Yes    
Collective-Bargaining Agreement Expiration Date Between August 31, 2014 and November 29, 2017