Shareholders' Equity (Narrative) (Details) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	1 Months Ended	12 Months Ended
	Oct. 29, 2011	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Shareholders' Equity [Line Items]
Repurchases of common stock (value)		$ 987,037,000	$ 273,067,000	$ 30,656,000
Stock Repurchase Plan [Member]
Shareholders' Equity [Line Items]
Stock available for repurchases under stock repurchase plan		500,000,000
Stock repurchase program, authorized amount	500,000,000
Repurchases of common stock (shares)		28,500	10,100	1,100
Repurchases of common stock (value)		975,900,000	263,500,000	23,100,000
Weighted average price per share of stock repurchased in period		$ 34.21	$ 25.97	$ 20.79
Value of shares withheld to satisfy employee tax withholding obligations		$ 11,100,000	$ 9,500,000	$ 7,600,000