Common Stock and Treasury Stock - Additional Information (Detail) - USD ($)	3 Months Ended	63 Months Ended
	Mar. 31, 2017	Mar. 31, 2017	Feb. 28, 2014	Jul. 31, 2013	Sep. 13, 2012	Sep. 12, 2012
Maximum stock authorized to purchase under stock repurchase program			$ 200,000,000			$ 262,100,000
Increase in maximum stock authorized to purchase under stock repurchase program			$ 100,000,000	$ 100,000,000
Repurchase of common stock, shares	0	40,129,393
Repurchase of common stock, value		$ 455,900,000
Maximum
Maximum stock authorized to purchase under stock repurchase program					$ 113,000,000
Stock authorized to purchase under stock repurchase program, shares					7,500,000
Remaining value of shares authorized for purchase under the stock repurchase program	$ 78,200,000	$ 78,200,000