Summary of Significant Accounting Policies - Summary of Property and Equipment and Related Accumulated Depreciation (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment	$ 3,629	$ 3,054
Less accumulated depreciation	(695)	(442)
Net property and equipment	$ 2,934	2,612
Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful life	7 years
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful life	3 years
Gross property, plant and equipment	$ 495	476
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful life	5 years
Gross property, plant and equipment	$ 800	729
Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful life	7 years
Gross property, plant and equipment	$ 72	50
Leasehold improvements
Property, Plant and Equipment [Line Items]
Leasehold improvements, Useful Life	Shorter of the useful life or remaining lease term (10 years)
Gross property, plant and equipment	$ 2,226	1,763
Leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful life	10 years
Office equipment under capital lease
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful life	3 years
Gross property, plant and equipment	$ 36	$ 36