Fair Value Measurements - Liabilities (Details) - Recurring - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value Measurements
Acquisition-related contingent consideration - short-term		$ 43,397
Acquisition-related contingent consideration - long-term		7,800
Liabilities	$ 11,500	51,197
Level 3
Fair Value Measurements
Acquisition-related contingent consideration - short-term		43,397
Acquisition-related contingent consideration - long-term		7,800
Liabilities	$ 11,500	$ 51,197