Commitments and Contingencies - Rent Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Rent expense under operating leases	$ 2.2
Rent expense under operating leases		$ 2.0	$ 1.0