Employee Benefit Plans (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Activity under all stock option incentive plans
Balance at December 31, 2011, Number of Shares	66
Balance at December 31, 2011, Weighted Average Exercise Price per Share (usd per share)	$ 27.47
Balance at December 31, 2011, Weighted Average Grant-Date Fair Value per Share (usd per share)	$ 15.10
Options assumed, Number of Shares	4
Options assumed, Weighted Average Exercise Price per Share (usd per share)	$ 9.71
Options assumed, Weighted Average Grant-Date Fair Value per Share (usd per share)	$ 27.54
Options cancelled, Number of Shares	(1)
Options cancelled, Weighted Average Exercise Price per Share (usd per share)	$ 35.82
Options cancelled, Weighted Average Grant-Date Fair Value per Share (usd per share)	$ 12.83
Options exercised, Number of Shares	(9)
Options exercised, Weigthed Average Exercise Price per Share (usd per share)	$ 16.83
Options Exercised, Weighted Average Grant-Date Fair Value per Share (usd per share)	$ 11.85
Balance at September 30, 2012, Number of Shares	60
Balance at September 30, 2012, Weighted Average Exercise Price per Share (usd per share)	$ 27.77
Balance at September 30, 2012, Weighted Average Grant-Date Fair Value per Share (usd per share)	$ 14.93