Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Recurring basis - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Liabilities
Bookings Commitment	$ 25,710	$ 21,983
Interest make-whole derivative	63	0
Quoted price in active markets for identical assets (Level 1)
Liabilities
Bookings Commitment	0	0
Interest make-whole derivative	0	0
Significant other observable inputs (Level 2)
Liabilities
Bookings Commitment	0	0
Interest make-whole derivative	0	0
Significant unobservable inputs (Level 3)
Liabilities
Bookings Commitment	25,710	21,983
Interest make-whole derivative	$ 63	$ 0