Equity-Based Compensation - Schedule of Activity Related to Stock Option Awards (Detail)	12 Months Ended
	Dec. 31, 2017 $ / shares shares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Options, Outstanding, Beginning Balance | shares	3,441,900
Options, Forfeited | shares	(415,400)
Options, Expired | shares	(102,462)
Options, Exercised | shares	(590)
Options, Outstanding, Ending Balance | shares	2,923,448
Options, Exercisable at December 31, 2017 | shares	1,205,227
Weighted Average Exercise Price, Outstanding, Beginning Balance | $ / shares	$ 18.67
Weighted Average Exercise Price, Forfeited | $ / shares	18.04
Weighted Average Exercise Price, Expired | $ / shares	18.16
Weighted Average Exercise Price, Exercised | $ / shares	18.67
Weighted Average Exercise Price, Outstanding, Ending Balance | $ / shares	18.78
Weighted Average Exercise Price, Exercisable at December 31, 2017 | $ / shares	$ 19.01
Weighted Average Remaining Contractual Life, Outstanding at December 31, 2017	7 years 7 months 24 days
Weighted Average Remaining Contractual Life, Exercisable at December 31, 2017	7 years 6 months 7 days