Fair Value Measurements - Assets and liabilities that were recognized at fair value on a recurring basis (Details) - Recurring - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Liabilities
Contingent stock liability	$ 64,660
Total	76,452	$ 13,878
Earn-out
Liabilities
Earn out liability	3,610	11,100
Level 2
Liabilities
Contingent stock liability	64,660
Total	72,842	2,778
Level 3
Liabilities
Total	3,610	11,100
Level 3 | Earn-out
Liabilities
Earn out liability	3,610	11,100
Interest rate swap asset
Liabilities
Interest rate swap liability	8,182	$ 2,778
Interest rate swap asset | Level 2
Liabilities
Interest rate swap liability	$ 8,182