Equity-Based Compensation - Number and Weighted Average Grant Date Fair Value of Equity Awards Granted (Details) (USD $) In Thousands, except Per Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Stock Appreciation Rights (SARs) [Member]
Equity instruments other than options, grants in period	270	26	305	40
Equity instruments other than options, grants in period, weighted average grant date fair value	$ 10.30	$ 16.45	$ 10.34	$ 16.85
Restricted Stock Units (RSUs) [Member]
Equity instruments other than options, grants in period	245	83	290	134
Equity instruments other than options, grants in period, weighted average grant date fair value	$ 26.52	$ 38.96	$ 26.80	$ 40.67