Commitments and Contingencies - Employment Contracts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Other Commitments [Line Items]
Severance costs	$ 1,783	$ 3,732
Payments for Severance	(4,215)	(929)
Remaining severance liability	371	2,803	$ 0
Selling and Marketing Expense
Other Commitments [Line Items]
Severance costs	500
Technology And Development
Other Commitments [Line Items]
Severance costs	$ 1,300
Employment Contracts
Other Commitments [Line Items]
Period of severance obligations (up to)	12 months
Remaining severance liability	$ 200
Employment Contracts | Former CEO
Other Commitments [Line Items]
Bonus		100
Severance costs		500
Annual fee		100
Remaining severance liability	200	900
Employment Contracts | Former Executive-Level Employees
Other Commitments [Line Items]
Severance costs		2,500
Remaining severance liability	$ 0	1,900
Employment Contracts | Sales and Marketing and General and Administrative Expenses
Other Commitments [Line Items]
Liquidity bonuses			$ 2,600
Employment Contracts | General and Administrative Expenses | Former CEO
Other Commitments [Line Items]
Severance costs		900
Employment Contracts | General and Administrative Expenses | Former Executive-Level Employees
Other Commitments [Line Items]
Severance costs		1,700
Employment Contracts | Selling and Marketing Expense | Former Executive-Level Employees
Other Commitments [Line Items]
Severance costs		400
Employment Contracts | Technology And Development | Former Executive-Level Employees
Other Commitments [Line Items]
Severance costs		$ 400