Stockholders' Equity - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Par value of common stock repurchased	$ 0.01	$ 0.01
Total amount authorized for repurchase under company's stock repurchase program	$ 50,000,000
Number of shares of common stock repurchased during period	0		1,540,813
Aggregate cost			27,000,000
Average cost per share of common stock repurchased during period			$ 17.52
Remaining amount authorized for repurchase under company's stock repurchase program	22,500,000
Common stock reserved and available for issuance	1,500,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures	0
Compensation expense related to stock options	0
Vesting period of non-vested shares	5 years
Total unrecognized compensation cost related to nonvested shares of common stock granted	7,800,000
Weighted average period of cost recognized	3 years 1 month 10 days
Total fair value of shares of common stock vested		3,900,000	3,700,000
Compensation expense related to nonvested stock grants	$ 4,100,000	$ 3,900,000	$ 4,400,000
Price of shares issued under Employee Stock Purchase Plan as a percentage of FMV	95.00%
Number of shares reserved for the Employee Stock Purchase Plan	250,000
Shares redeemed to satisfy personal tax obligations	40,716	40,608	36,621
Employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Nonvested stock grants to employees	172,545	198,243	187,140
Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non vested stock grants to Independent director	26,900	24,300	26,100