Treasury Stock - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2015	Jun. 30, 2014	Mar. 17, 2015	Feb. 09, 2015
Equity, Class of Treasury Stock [Line Items]
Remaining authorized repurchase amount	$ 106,000	$ 106,000
Modified Dutch Auction Authorized Amount					$ 200,000
Fees and Expenses Modified Dutch Auction				$ 700
Repurchase of common stock under share repurchase authorization		$ (170,132)	$ (7,735)
Treasury stock (shares)	27,176,938	27,176,938
Common Stock Purchased Through Modified Dutch Auction Tender Offer Shares				2,766,354
Common Stock Purchased Through Modified Dutch Auction Tender Offer Price Per Share				$ 58.50
Common Stock Purchased Through Modified Dutch Auction Tender Offer Value				$ 161,800
2004 Stock Incentive Plan [Member]
Equity, Class of Treasury Stock [Line Items]
Average cost per share of treasury stock acquired		$ 57.53
Treasury shares issued (shares)		125,846
Issuance of treasury shares, average cost per share (usd per share)		$ 6.30
Shares repurchased to satisfy minimum employee withholding tax requirements resulting from the vesting of such restricted stock units (shares)		44,122
Stock Repurchase Program [Member]
Equity, Class of Treasury Stock [Line Items]
Repurchases of common stock (in shares)	139,421
Average cost per share of treasury stock acquired	$ 54.71
Repurchase of common stock under share repurchase authorization	$ (7,600)