Summary of Significant Accounting Policies - Rollforward of Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Doubtful Accounts
Beginning balance	$ 2,081	$ 565
Charged to operating expenses	1,963	1,757	$ 565
Write offs of accounts receivable	(341)	(241)
Ending balance	$ 3,703	$ 2,081	$ 565