Income Taxes - Income Taxes Computed at Federal Statutory and Provision Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income tax benefit at statutory rate	$ (10,574)	$ (13,832)	$ (11,089)
State taxes, net of federal benefit	(213)	14	10
Impact of foreign income taxes	2,124	119	73
Stock-based compensation	2,340	1,629	1,043
Foreign exchange gain	(1,920)	0	0
Change in valuation allowance	9,510	12,673	10,434
Research and development credits	(764)	(674)	(408)
Other	(51)	180	193
Provision for income taxes	$ 452	$ 109	$ 256