Fair Value Measurements (Details 2) (Recurring basis, Level 3, USD $)	12 Months Ended
	Dec. 31, 2012
Fair Value Measurements
Put option liability	$ 30,415
Put option liability
Fair Value Measurements
Put option liability	$ 30,415
Put option liability | Probability-adjusted discounted cash flow
Fair Value Measurements
Discount rate (as a percent)	12.00%
Put option liability | Probability-adjusted discounted cash flow | Minimum
Fair Value Measurements
Probabilities of success (as a percent)	25.00%
Put option liability | Probability-adjusted discounted cash flow | Maximum
Fair Value Measurements
Probabilities of success (as a percent)	45.00%
Put option liability | Probability-adjusted discounted cash flow | Weighted Average
Fair Value Measurements
Probabilities of success (as a percent)	35.00%