Commitments and Contingencies - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Sublease
Future commitments and obligations under operating lease
Sublease term	3 years
Future annual sublease rental income	$ 0.3
Leases
Rent payment received	0.1	$ 0.1
Real Estate and Office Equipment
Operating lease expense	$ 0.6