Share Repurchase Programs - Additional Information (Detail) - USD ($)		1 Months Ended	2 Months Ended		4 Months Ended	6 Months Ended			10 Months Ended		35 Months Ended
	Feb. 13, 2015	Aug. 31, 2014	Feb. 16, 2017	Feb. 19, 2016	Jun. 30, 2017	Jun. 30, 2017	Jun. 30, 2016	Feb. 13, 2015	Dec. 31, 2016	Dec. 31, 2015	Jun. 30, 2017	Feb. 20, 2015	Aug. 06, 2014
Equity, Class of Treasury Stock [Line Items]
Amount paid to counter party under share repurchase program						$ 38,567,000	$ 54,130,000
Common stock repurchased (in shares)											13,272,020
Share repurchase, weighted average price (in dollars per share)											$ 34.31
Common stock repurchased, value						$ 38,567,000
ASR Program
Equity, Class of Treasury Stock [Line Items]
Percentage of common shares initially delivered under share repurchase program (as a percent)													80.00%
Share repurchase, weighted average price (in dollars per share)								$ 31.49
ASR Program | JP Morgan Securities LLC
Equity, Class of Treasury Stock [Line Items]
Share repurchase, amount authorized													$ 200,000,000
Amount paid to counter party under share repurchase program		$ 200,000,000						$ 200,000,000
Common stock repurchased (in shares)	784,694	5,567,154						6,351,848
New Share Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Share repurchase, amount authorized												$ 200,000,000
Common stock repurchased (in shares)				497,094						2,751,454
Share repurchase, weighted average price (in dollars per share)				$ 35.45						$ 39.55
Common stock repurchased, value				$ 17,622,000						$ 108,821,000
Share repurchase, remaining amount authorized										$ 91,261,000
Amended Share Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Share repurchase, amount authorized				200,000,000
Common stock repurchased (in shares)			383,690						2,630,433
Share repurchase, weighted average price (in dollars per share)			$ 36.70						$ 34.36
Common stock repurchased, value			$ 14,080,000						$ 90,377,000
Share repurchase, remaining amount authorized				$ 73,654,000					$ 109,702,000
Share Repurchase Program 2017
Equity, Class of Treasury Stock [Line Items]
Share repurchase, amount authorized			300,000,000
Common stock repurchased (in shares)					657,501	1,041,191
Share repurchase, weighted average price (in dollars per share)					$ 37.24	$ 37.04
Common stock repurchased, value					$ 24,488,000	$ 38,567,000
Share repurchase, remaining amount authorized			$ 95,634,000