Stock-Based Compensation - Rollforward of Share Activity (Details) (USD $)	12 Months Ended
	Dec. 31, 2011
Stock Options [Member]
Share activity [Line Items]
Options outstanding, beginning of period	1,499,000
Options granted	304,000
Option forfeitures	(21,000)
Option expirations	(37,000)
Options exercised	(821,000)
Options outstanding, end of period	924,028
Weighted average exercise price of options, beginning of period	$ 23.27
Weighted average exercise price of options granted	$ 38.45
Weighted average exercise price of options forfeited	$ 24.70
Weighted average exercise price of option expriations	$ 32.90
Weighted average exercise price of options exercised	$ 22.98
Weighted average exercise price of options, end of period	$ 28.13
Restricted Stock Units (RSUs) [Member]
Share activity [Line Items]
Restricted stock units unvested, beginning of period	821,000
Restricted stock units granted	401,000
Restricted stock units forfeited	(52,000)
Restricted stock units vested	(312,000)
Restricted stock units unvested, end of period	857,582
Weighted average grant date fair value of restricted stock units, beginning of period	$ 24.97
Weighted average grant date fair value of restricted stock units granted	$ 38.70
Weighted average grant date fair value restricted stock units forfeited	$ 25.16
Weighted average grant date fair value of restricted stock unit vests	$ 25.99
Weighted average grant date fair value of restricted stock units, end of period	$ 31.00