Share-Based Payments (Details 9) (Performance vested restricted stock units, USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Performance vested restricted stock units
Performance-Vested Restricted Stock Units (PVRSUs)
Beginning Balance, Unvested, Shares	47,000
Beginning Balance, Weighted Average Grant Date Fair Value	$ 49.34
Shares, Granted	0	1,000	4,000
Weighted Average Grant Date Fair Value, Granted	$ 0.00	$ 53.64	$ 53.64
Shares, Vested	(46,000)
Weighted Average Grant Date Fair Value, Vested	$ 119.03
Shares, Forfeited	(70)
Weighted Average Grant Date Fair Value, Forfeited	$ 49.65
Ending Balance, Unvested, Shares	930	47,000
Ending Balance, Weighted Average Grant Date Fair Value	$ 53.64	$ 49.34