| Income Taxes - Summary of Changes in Liability Related to Unrecognized Tax Benefits (Parenthetical) (Detail) - USD ($) $ in Millions | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013 | 
|---|---|---|---|---|
| Schedule Of Unrecognized Tax Benefits [Line Items] | ||||
| Accrued interest and penalties | $ 0.8 | $ 1.1 | $ 1.2 | $ 1.1 | 
| State and Local Jurisdiction [Member] | ||||
| Schedule Of Unrecognized Tax Benefits [Line Items] | ||||
| Net operating losses | $ 0.3 | $ 0.6 | $ 0.8 | 
| X | ||||||||||
| 
- Definition Schedule of unrecognized tax benefits. No definition available. 
 | 
| X | ||||||||||
| 
- Definition The amount of estimated penalties and interest accrued as of the balance sheet date arising from income tax examinations. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
 | 
| X | ||||||||||
| 
- Definition Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
 | 
| X | ||||||||||
| 
- Details 
 |