Long-Term Incentive Plan (Details) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended						12 Months Ended
	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010	Dec. 31, 2009	Jun. 30, 2009	Dec. 31, 2010 Y	Dec. 31, 2011 Performance-based Restricted Stock Units [Member] Y
Status of, and Changes in, Performance-based Restricted Stock Units [Abstract]
Outstanding balance at December 31, 2010, shares								0
Outstanding balance at December 31, 2010, Weighted average grant date fair value								$ 0.00
Granted at target level, Shares								78,131
Granted at target level, weighted average grant date fair value	$ 19.65	$ 12.34	$ 9.20	$ 7.69	$ 7.71	$ 8.36		$ 58.83
Adjustments above/(below) target level, Shares								19,313
Adjustments above/(below) target level, weighted average grant date fair value								$ 58.83
Expired, Shares								0
Expired, weighted average grant date fair value								$ 0
Forfeited, Shares								(879)
Forfeited, weighted average grant date fair value								$ 58.83
Outstanding balance at December 31, 2011, shares								96,565
Outstanding balance at December 31, 2011, Weighted average grant date fair value								$ 58.83
Vested units at December 31, 2011								0
Unvested units at December 31, 2011								96,565
Unrecognized compensation expense			$ 46,713				$ 46,713	$ 4,390
Weighted average remaining period (years)							1.36	2.17