Stockholders' Equity - Additional Information (Detail) - USD ($)		1 Months Ended		3 Months Ended			9 Months Ended
	Oct. 06, 2015	Jan. 31, 2015	Apr. 30, 2014	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Aug. 12, 2014
Stockholders Equity [Line Items]
Common stock, shares issued				90,305,888	90,191,100		90,305,888
Unvested shares of common stock				4,267,253			4,267,253
Treasury stock, shares				4,941,938	4,105,970		4,941,938
Dividends declared to common stockholders							$ 72,593,000
Dividends payable				$ 18,396,000	$ 172,000		$ 18,396,000
Share Repurchase Program, authorized amount									$ 250,000,000
Shares repurchased				835,968	855,970		835,968
Stock repurchased during period under Share Repurchase Program, average price per share				$ 17.92	$ 17.50
Stock repurchased during period, total cost				$ 15,000,000	$ 15,000,000		$ 15,000,000
Shares repurchased payment settlement during period		$ 5,650,000					20,650,000	$ 50,708,000
Share Repurchase Program, remaining authorized repurchase amount				220,000,000			220,000,000
Secondary offering costs				0		$ 0	0	$ 747,000
Treasury stock at cost				$ 124,871,000	$ 109,871,000		$ 124,871,000
Subsequent Event [Member]
Stockholders Equity [Line Items]
Dividends paid	$ 17,900,000
2.25x Performance Restricted Shares [Member]
Stockholders Equity [Line Items]
Unvested shares of common stock				1,370,821	1,451,453		1,370,821
Dividends payable on unvested restricted performance shares not probable of vesting							$ 2,820,000
2.75x Performance Restricted Shares [Member]
Stockholders Equity [Line Items]
Unvested shares of common stock				1,370,821	1,451,453		1,370,821
Dividends payable on unvested restricted performance shares not probable of vesting							$ 2,820,000
Bonus Performance Restricted Shares [Member]
Stockholders Equity [Line Items]
Unvested shares of common stock				433,940			433,940
Dividends payable on unvested restricted performance shares not probable of vesting							$ 261,000
Long-Term Incentive Performance Restricted Shares [Member]
Stockholders Equity [Line Items]
Unvested shares of common stock				67,606			67,606
Dividends payable on unvested restricted performance shares not probable of vesting							$ 43,000
Dividends on shares probable of vesting							12,000
Secondary Offering [Member]
Stockholders Equity [Line Items]
Common stock, shares issued			0
Shares repurchased			1,750,000
Shares offered and sold by the selling stockholders			17,250,000
Treasury stock at cost				$ 124,871,000	$ 109,871,000		$ 124,871,000