Debt (Details 2) (USD $)	9 Months Ended	3 Months Ended
	Sep. 30, 2011	Jun. 30, 2011 Convertible Notes	Mar. 31, 2011 Convertible Notes
Debt
Principal of notes tendered for conversion			$ 7,500,000
Conversion price of convertible notes (in dollars per share)		$ 50.59	$ 45.95
Notes tendered, cash paid		98,100,000	7,500,000
Notes tendered, shares issued upon conversion		1,660,095	111,318
Loss on extinguishment of debt	$ 3,349,000	$ 3,000,000	$ 300,000