Summary of Significant Accounting Policies - Contingent Consideration (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Contingent consideration disclosures
Undiscounted future contingent payments			$ 9,900	$ 12,700
Fair value measurement of contingent consideration
Fair value of short-term contingent consideration			6,892	9,354
Fair value of long-term contingent consideration			1,925	1,799
Liability for contingent consideration
Balance as of beginning of period		$ 8,817	11,153	92,426
Changes in fair value			696	(104)
Payments			(3,032)	(91,660)
Balance as of end of period			$ 8,817	11,153
Forecast
Liability for contingent consideration
Payments	$ (2,700)	$ (7,200)
TMG
Liability for contingent consideration
Acquisition				2,244
AFSC
Liability for contingent consideration
Acquisition				$ 8,247