Summary of Significant Accounting Policies - Prepaid Expenses and Other Current Assets, Property and Equipment and Impairment of Long-Lived Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Impairment of Long-Lived Assets
Impairment loss	$ 0
Computers and software
Property and Equipment
Useful life	3 years
Laboratory equipment office equipment and furniture
Property and Equipment
Useful life	5 years
Prepaid Expenses and Other Current Assets
Prepaid expenses and other current assets
Balance of deposit for supplies		$ 1,000