Stock Option Plan (Details 3) (USD $)	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, 2011 Non-vested restricted stock [Member]
Summary of non-vested restricted stock activity
Outstanding balance at December 31, 2010, shares							1,228,982
Outstanding balance at December 31, 2010, Weighted average grant date fair value							$ 29.89
Granted, shares							408,131
Granted, weighted average grant date fair value	$ 19.65	$ 12.34	$ 9.20	$ 7.69	$ 7.71	$ 8.36	$ 63.21
Vested, shares							(330,086)
Vested, weighted average grant date fair value							$ 31.81
Forfeited, shares							(17,894)
Forfeited, weighted average grant date fair value							$ 46.41
Outstanding balance at December 31, 2011, shares							1,289,133
Outstanding balance at December 31, 2011, Weighted average grant date fair value							$ 40.29