Related Party Transactions -Transactions with Stakeholders (Details) - Dealertrack - USD ($)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Cost of Revenue    
Related Party Transaction [Line Items]    
Costs under agreement $ 400,000 $ 2,000,000
Selling and Marketing Expense    
Related Party Transaction [Line Items]    
Costs under agreement $ 0 $ 300,000