Stock Repurchase Program (Detail) - USD ($) $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended				54 Months Ended
	Jun. 30, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jun. 30, 2015
Equity Class Of Treasury Stock [Line Items]
Number of shares repurchased as part of stock repurchase programs		4,994,578	15,812,566	7,185,257	1,150,000	29,502,401
Cost of shares repurchased	$ 12,391	$ 193,434	$ 436,419	$ 125,341	$ 19,138	$ 786,723
Weighted Average Price		$ 38.73	$ 27.60	$ 17.44	$ 16.64	$ 26.67
Repurchase Of Common Stock
Equity Class Of Treasury Stock [Line Items]
Number of shares repurchased as part of stock repurchase programs	360,000
Cost of shares repurchased	$ 12,391
Weighted Average Price	$ 34.42