Fair Value Fair Value - Probability of Put Liability (Details)	3 Months Ended
	Mar. 31, 2013
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Probability of put right being triggered	1.00%
Minimum
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Probability of put right being triggered	0.50%
Maximum
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Probability of put right being triggered	5.00%