Summary of Significant Accounting Policies - Trade Receivables (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Doubtful Accounts Receivable [Roll Forward]
Allowance for doubtful accounts, beginning balance	$ 1,610	$ 1,390	$ 1,120
Charged to costs and expenses	1,851	1,412	1,073
Amounts charged off, net	(1,829)	(1,192)	(803)
Allowance for doubtful accounts, ending balance	$ 1,632	$ 1,610	$ 1,390