Shareholders' Equity - Additional Information (Detail) - USD ($)	Sep. 02, 2014	Dec. 31, 2015	Nov. 11, 2015	Aug. 11, 2015	Jul. 20, 2015	Mar. 05, 2015	Dec. 31, 2014	Jun. 30, 2014
Accelerated Share Repurchases [Line Items]
Stock Repurchase Program, Authorized Amount		$ 100,000,000			$ 400,000,000			$ 25,000,000
Treasury stock shares (in shares)		7,430,000		3,059,629			2,385,000
Fair value of common stock repurchased		$ 238,775,000					$ 75,025,000
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]
Shares repurchased, aggregate repurchase amount			$ (75,000,000)
Treasury stock shares (in shares)			1,985,981
Fair value of common stock repurchased			$ 63,750,000