Income Taxes - Provision for Income Taxes, Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loss before provision for income taxes:
Domestic	$ (14,412)	$ (41,611)	$ (22,248)
Foreign	(6,419)	(1,136)	(898)
Loss before provision for income taxes	(20,831)	(42,747)	(23,146)
Provision for current income taxes:
U.S. state and local	(37)	361	328
Foreign	245	183	15
Total provision for current income taxes	208	544	343
Benefit for deferred income taxes:
Foreign	(92)	(61)
Total benefit for deferred income taxes	(92)	(61)
Total provision for income taxes	$ 116	$ 483	$ 343
Reconciliation between the U.S. federal statutory income tax rate to the effective tax rate, by applying such rates to loss before income tax provision
U.S. federal statutory income tax rate (as a percent)	(34.00%)	(34.00%)	(34.00%)
State income tax rate, net of U.S. federal tax benefit (as a percent)	(0.18%)	0.85%	0.94%
Stock-based compensation expense (as a percent)	1.40%	1.06%	2.70%
Acquisition related costs (as a percent)	5.77%
Mark-to-market expense (as a percent)	2.04%
Change in income tax rates (as a percent)	3.04%	0.35%	1.73%
Change in deferred tax asset valuation (as a percent)	21.12%	14.91%	28.71%
Goodwill impairment charge (as a percent)		16.61%
Other (as a percent)	1.37%	1.35%	1.40%
Effective tax rate (as a percent)	0.56%	1.13%	1.48%