Common Stock Repurchase Programs - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 11, 2017	Nov. 09, 2015
Share Repurchase Program 2013 [Member]
Stock Repurchase Program [Line Items]
Repurchase of common stock, authorized amount						$ 150,000,000
Aggregate shares repurchased	300,000	400,000	1,000,000	1,400,000
Aggregate purchase price	$ 12,500,000	$ 18,000,000	$ 47,000,000	$ 57,700,000
Common stock repurchase authorization expiration date			Dec. 31, 2018
Share Repurchase Program 2015 [Member]
Stock Repurchase Program [Line Items]
Remaining available authorized repurchase amount					$ 28,800,000
Share Repurchase Program 2017 [Member]
Stock Repurchase Program [Line Items]
Repurchase of common stock, authorized amount	153,800,000		$ 153,800,000		$ 125,000,000
Net Share Settlement [Member]
Stock Repurchase Program [Line Items]
Value of shares surrendered to satisfy tax withholding obligations	$ 3,100,000	$ 3,400,000	$ 10,000,000	$ 7,600,000
Net Share Settlement [Member] | Maximum [Member]
Stock Repurchase Program [Line Items]
Aggregate shares repurchased	100,000	100,000	200,000	200,000