Equity (Detail) - Share Repurchase Activity - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Stockholders' Equity Note [Abstract]
Number of shares repurchased (in shares)		210,012	1,124,117	5,538,612	5,350,915
Cash paid for repurchased shares during the quarter	$ 2,700	$ 11,558	$ 79,678	$ 453,000	$ 387,126