Summary of Significant Accounting Policies - Changes in Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Doubtful Accounts Receivable [Roll Forward]
Balance at beginning of period	$ 1,060	$ 1,062	$ 1,117
Charged to expense	(5)	40	42
Deductions	(795)	(38)	(91)
Effect of foreign currency exchange rates	7	(4)	(6)
Balance at end of period	$ 267	$ 1,060	$ 1,062