Common Stock and Share-Based Compensation - Summary of Restricted Stock Unit Activity (Detail) - RSUs	9 Months Ended
	Sep. 30, 2015 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding at beginning balance, in shares	1,011,129
Stock units issued, in shares	419,222
Shares issued upon vesting of stock units, in shares	(224,784)
Stock units canceled or forfeited, in shares	(95,380)
Outstanding at ending balance, in shares	1,110,187
Weighted average grant date fair value | $ / shares	$ 15.34
Employees
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding at beginning balance, in shares	898,550
Stock units issued, in shares	374,401
Shares issued upon vesting of stock units, in shares	(162,061)
Stock units canceled or forfeited, in shares	(93,751)
Outstanding at ending balance, in shares	1,017,139
Weighted average grant date fair value | $ / shares	$ 15.37
Non-Employee Directors
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Outstanding at beginning balance, in shares	112,579
Stock units issued, in shares	44,821
Shares issued upon vesting of stock units, in shares	(62,723)
Stock units canceled or forfeited, in shares	(1,629)
Outstanding at ending balance, in shares	93,048
Weighted average grant date fair value | $ / shares	$ 15.04