Summary of Significant Accounting Policies - Accounts Receivable and Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
Accounts receivable, gross	$ 4,133	$ 5,056
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance Beginning of the Year	3,133	2,511	$ 2,309
Additions	6,704	11,237	9,826
Write-offs Net of Recoveries	(6,925)	(10,615)	(9,624)
Balance at End of Year	$ 2,912	$ 3,133	$ 2,511