Fair Value Put Level 3 Inputs (Details) (Derivative Liability, Income Approach Valuation Technique, Level 3, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012
Derivative Liability | Income Approach Valuation Technique | Level 3
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Equity-risk premium	6.50%
Risk premium	12.90%
Size premium	3.90%
Growth rate	1.00%
Equity-risk premium, Effect of 1% increase	$ (0.8)	[1]
Risk premium, Effect of 1% increase	(0.4)	[1]
Size premium, Effect of 1% increase	(0.4)	[1]
Growth rate, Effect of 1% increase	0.3	[1]
Equity-risk premium, Effect of 1% decrease	1.0	[1]
Risk premium, Effect of 1% decrease	0.4	[1]
Size premium, Effect of 1% decrease	0.5	[1]
Growth rate, Effect of 1% decrease	$ (0.3)	[1]

[1] Assuming all other inputs are unchanged.