Common Stock and Share-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Options (in shares)
Options outstanding, beginning balance, in shares	3,691,567
Granted, in shares	0	0
Forfeited and canceled, in shares	(301,471)
Exercised, in shares	(135,991)
Options outstanding, ending balance, in shares	3,254,105
Options exercisable, balance, in shares	3,251,576
Weighted Average Exercise Price (in dollars per share)
Options outstanding, beginning balance, Weighted average exercise price (in dollars per share)	$ 20.13
Granted, Weighted average exercise price (in dollars per share)	0.00
Forfeited and canceled, Weighted average exercise price, dollars per share (in dollars per share)	22.25
Exercised, Weighted average exercise price (in dollars per share)	16.28
Options outstanding, ending balance, Weighted average exercise price (in dollars per share)	20.10
Options exercisable, ending balance, Weighted average exercise price (in dollars per share)	$ 20.11
Options, Additional Disclosures
Options outstanding, ending balance, Weighted Average Contractual Life	2 years 4 months 6 days
Options exercisable, ending balance, Weighted Average Contractual Life	2 years 4 months 2 days
Options outstanding, ending balance, Aggregate Intrinsic Value	$ 3,241,791
Options exercisable, ending balance, Aggregate Intrinsic Value	$ 3,235,620