Income Taxes Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net loss before income taxes:
Net loss before income taxes	$ (98,866)	$ (74,224)	$ (48,133)
Current:
United States	193	139	0
Other	0	0	0
Current Income Tax Expense (Benefit)	193	139	0
Deferred:
United States	0	0	0
Other	0	0	0
Deferred Income Tax Expense (Benefit)	0	0	0
Income Tax Expense (Benefit)	$ 193	$ 139	$ 0
Effective tax rate (in percentage)	(0.19%)	(0.19%)	0.00%
United States
Net loss before income taxes:
Net loss before income taxes	$ (88,123)	$ (59,211)	$ (48,133)
Other
Net loss before income taxes:
Net loss before income taxes	$ (10,743)	$ (15,013)	$ 0