Summary of Significant Accounting Policies - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Changes in accumulated other comprehensive income, net of tax
Balance at the beginning of period	$ (1,431)
Other comprehensive loss and pension reclassification	(848)	$ (2,707)	$ (4,463)
Balance at the end of period	(2,279)	(1,431)
Foreign currency
Changes in accumulated other comprehensive income, net of tax
Balance at the beginning of period	(744)
Other comprehensive loss and pension reclassification	(847)
Balance at the end of period	(1,591)	(744)
Defined benefit pension plan
Changes in accumulated other comprehensive income, net of tax
Balance at the beginning of period	(687)
Other comprehensive loss and pension reclassification	(1)
Balance at the end of period	$ (688)	$ (687)