Common Stock Repurchase Programs - Additional Information (Detail) - Share Repurchase Program Two Thousand And Thirteen [Member] - USD ($) shares in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2015	Dec. 31, 2014	Nov. 06, 2013
Stock Repurchase Program [Line Items]
Repurchase of common stock, authorized amount				$ 200,000,000
Common stock repurchase authorization expiration date		2016-11
Aggregate shares purchased	0.4	1.0	1.8
Aggregate purchase price	$ 18,400,000	$ 40,400,000	$ 76,800,000