Common and Preferred Stock (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended		3 Months Ended
	Dec. 01, 2015	Apr. 30, 2017	Apr. 30, 2016	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Subsequent Event [Line Items]
Increase in share repurchase authorized amount	$ 300,000
Purchase of common stock (in shares)				82,000	628,000
Repurchase of common stock, including subsequent settlements				$ 7,600	$ 45,800
Purchase of common stock			$ 1,200	7,005	$ 46,864
Remaining authorized repurchase amount				$ 572,400
Common stock, authorized (in shares)				150,000,000		150,000,000
Common stock, par value (in dollars per share)				$ 0.01		$ 0.01
Preferred stock, authorized (in shares)				5,000,000		5,000,000
Preferred stock, par value (in dollars per share)				$ 0.01		$ 0.01
Preferred stock, issued (in shares)				0		0
Subsequent Event
Subsequent Event [Line Items]
Purchase of common stock		$ 600