Stockholder's Equity - Additional Information (Detail) (USD $)	1 Months Ended					12 Months Ended			0 Months Ended
	Nov. 30, 2014	Aug. 31, 2014	May 31, 2014	Feb. 28, 2014	Feb. 18, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014
Equity, Class of Treasury Stock
Common stock, shares authorized						400,000,000	400,000,000		400,000,000
Common stock, par value						$ 0.01	$ 0.01		$ 0.01
Common stock, shares outstanding						101,439,297	101,192,408		101,439,297
Common stock, voting rights						one vote
Net cost for common stock purchased						$ 2,062,000	$ 15,472,000	$ 911,000
Stock repurchases, shares						9,578	114,355	7,640
Dividend paid	$ 1.50	$ 1.25	$ 1.25	$ 1.25
Additional dividend paid	$ 1.00
Preferred stock, shares authorized						40,000,000	40,000,000		40,000,000
Preferred stock, par value						$ 0.01	$ 0.01		$ 0.01
Preferred stock, shares issued						0	0		0
Common shares redeemed and canceled					24,549,222
Equity Repurchase Program
Equity, Class of Treasury Stock
Repurchase of equity amount authorized						1,700,000,000			1,700,000,000
Net cost for common stock purchased									$ 1,100,000,000
Stock repurchases, shares						0	0	0	12,804,954