Stock-Based Compensation (Summary of the Company's Restricted Stock Unit Activity) (Details) (Restricted Stock [Member], USD $)	12 Months Ended
	Dec. 31, 2012
Restricted Stock [Member]
Number of Units Outstanding as of January 1, 2012	2,197,460
Number of Units Granted	836,835
Number of Units Vested	(893,739)
Number of Units Forfeited	172,003
Outstanding as of December 31, 2012	1,968,553
Expected to vest, net of estimated forfeitures, as of December 31, 2012	1,898,708
Weighted Average Grant Date Fair Value Outstanding as of January 1, 2012	$ 42.39
Weighted Average Grant Date Fair Value Granted	$ 62.34
Weighted Average Grant Date Fair Value Vested	$ 39.75
Forfeitures	$ 48.20
Weighted Average Grant Date Fair Value Outstanding as of December 31, 2012	$ 51.56
Expected to vest, net of estimated fofeitures, as of December 31, 2012	$ 51.37