Shareholders' Equity - Additional Information (Detail) - USD ($)	Sep. 02, 2014	Dec. 31, 2016	Jan. 06, 2016	Dec. 31, 2015	Nov. 11, 2015	Aug. 11, 2015	Jul. 20, 2015	Mar. 05, 2015	Jun. 30, 2014
Accelerated Share Repurchases [Line Items]
Stock Repurchase Program, Authorized Amount		$ 100,000,000	$ 375,000,000				$ 400,000,000		$ 25,000,000
Shares repurchased, aggregate repurchase amount					$ (75,000,000)
Treasury stock shares (in shares)		8,003,000	363,209	7,430,000		3,059,629
Fair value of common stock repurchased		$ 257,683,000		$ 238,775,000
Accelerated Share Repurchase Agreement
Accelerated Share Repurchases [Line Items]
Shares repurchased, aggregate repurchase amount	$ 50,000,000
Total number of shares repurchased (in shares)	1,539,760
Second Accelerated Share Repurchase Agreement
Accelerated Share Repurchases [Line Items]
Shares repurchased, aggregate repurchase amount								$ 100,000,000
Treasury stock shares (in shares)						391,637		2,667,992
Fair value of common stock repurchased								$ 85,000,000
Third Accelerated Share Repurchase Agreement [Member]
Accelerated Share Repurchases [Line Items]
Treasury stock shares (in shares)					1,985,981
Fair value of common stock repurchased					$ 63,750,000