Summary of Restricted Stock and Performance Share Units Activity (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013	Dec. 31, 2012
Restricted Stock
Restricted Stock
Beginning Balance (In Shares)	682,000
Granted (In Shares)	548,000		307,000	368,000
Vested (In Shares)	(365,000)
Forfeited (In Shares)	(167,000)
Ending Balance (In Shares)	698,000	[1]	682,000
Weighted Average Grant Price
Beginning Balance (In Dollars Per Share)	$ 25.77
Granted (In Dollars Per Share)	$ 29.11		$ 29.23	$ 26.08
Vested (In Dollars Per Share)	$ 24.21
Forfeited (In Dollars Per Share)	$ 27.69
Ending Balance (In Dollars Per Share)	$ 28.75	[1]	$ 25.77
Performance Share Units
Restricted Stock
Beginning Balance (In Shares)	0
Granted (In Shares)	167,000
Vested (In Shares)	(36,000)
Forfeited (In Shares)	(20,000)
Ending Balance (In Shares)	111,000	[1]
Weighted Average Grant Price
Beginning Balance (In Dollars Per Share)	$ 0.00
Granted (In Dollars Per Share)	$ 32.14
Vested (In Dollars Per Share)	$ 32.48
Forfeited (In Dollars Per Share)	$ 32.22
Ending Balance (In Dollars Per Share)	$ 32.01	[1]

[1] The outstanding non-vested restricted stock as of December 31, 2014 includes 75,000 shares that are subject to performance conditions.