Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Liabilities
Bookings Commitment	$ 1,625	$ 1,122
Recurring basis
Liabilities
Bookings Commitment	24,553	21,983
Interest make-whole derivative	7	0
Recurring basis | Quoted price in active markets for identical assets (Level 1)
Liabilities
Bookings Commitment	0	0
Interest make-whole derivative	0	0
Recurring basis | Significant other observable inputs (Level 2)
Liabilities
Bookings Commitment	0	0
Interest make-whole derivative	0	0
Recurring basis | Significant unobservable inputs (Level 3)
Liabilities
Bookings Commitment	24,553	21,983
Interest make-whole derivative	$ 7	$ 0