Variable Interest Entity (Details) (Variable Interest Entity, Primary Beneficiary, USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2013
Mar. 01, 2012
Dec. 16, 2011
Variable Interest Entity, Primary Beneficiary
     
Variable Interest Entity [Line Items]      
Initial capital contribution     $ 5.0
Ownership percentage   40.00% 20.00%
Additional capital contribution due to achievement of milestones   5.0  
Minimum purchase price to exercise all call options on outstanding interest $ 50.0