Fair Value Measurements - Liabilities (Details) - Recurring - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value Measurements
Acquisition-related contingent consideration - short-term	$ 15,224	$ 1,493
Acquisition-related contingent consideration - long-term	13,652	1,515
Liabilities	28,876	3,008
Level 3
Fair Value Measurements
Acquisition-related contingent consideration - short-term	15,224	1,493
Acquisition-related contingent consideration - long-term	13,652	1,515
Liabilities	$ 28,876	$ 3,008