Stockholders' Equity (Stock Option Activity) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 Y
Summary of Stock Option Activity [Roll Forward]
Number of Shares, Outstanding, Beginning Balance	5,513
Number of Shares, Granted	767
Number of Shares, Exercised	(316)
Number of Shares, Cancelled	(35)
Number of Shares, Outstanding, Ending Balance	5,929
Number of shares, Exercisable, Ending Balance	3,737
Weighted Average Exercise Price, Outstanding, Beginning Balance	$ 50.80
Weighted Average Exercise Price, Granted	$ 68.39
Weighted Average Exercise Price, Exercised	$ 45.09
Weighted Average Exercise Price, Cancelled	$ 59.00
Weighted Average Exercise Price, Outstanding, Ending Balance	$ 53.33
Weighted Average Exercise Price, Exercisable, Ending Balance	$ 49.97
Weighted Average Remaining Contractual Term, Outstanding, Ending Balance	4.1
Weighted Average Remaining Contractual Life (Years)	3.1
Aggregate Intrinsic Value, Outstanding, Ending Balance	$ 80,823
Aggregate Intrinsic Value, Exercisable, Ending Balance	$ 62,235