Goodwill and Acquired Intangible Assets - Acquired Intangible Assets Subject to Amortization (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Finite Lived Intangible Assets [Line Items]
Cost	$ 15,800	$ 15,800
Accumulated Amortization	(7,628)	(3,740)
Foreign Currency Translation Adjustments	(222)	(356)
Net	7,950	11,704
Developed technology
Finite Lived Intangible Assets [Line Items]
Cost	14,000	14,000
Accumulated Amortization	(6,584)	(3,133)
Foreign Currency Translation Adjustments	(169)	(279)
Net	$ 7,247	$ 10,587
Remaining Useful Life	2 years 10 months 24 days	3 years 8 months 2 days
Customer relationships
Finite Lived Intangible Assets [Line Items]
Cost	$ 1,800	$ 1,800
Accumulated Amortization	(1,044)	(606)
Foreign Currency Translation Adjustments	(53)	(78)
Net	$ 703	$ 1,117
Remaining Useful Life	2 years 3 months 2 days	3 years 1 month 2 days