Business Combinations - Additional Information (Details) $ in Thousands, shares in Millions	3 Months Ended
	Mar. 31, 2021 USD ($) clientList shares	Mar. 31, 2020 USD ($) clientList shares	Dec. 31, 2020 USD ($)
Business Acquisition, Contingent Consideration [Line Items]
Consideration paid in cash	$ 1,900	$ 9,400
Contingent consideration	1,600	4,800
Contingent consideration arrangements - High	1,700	6,200
Aggregate fair value of contingent consideration	1,600	4,700
Contingent consideration, current	22,767		$ 20,288
Contingent consideration, non-current	31,463		$ 34,103
Annual revenue	3,600	6,100
Consideration paid in common stock		900
Goodwill	1,500	11,200
Business combination contingent consideration liability other adjustments based on projected future results of acquisition	700	(700)
Consideration paid in cash	$ 1,500	$ 2,400
Number of common stock issued (in shares) | shares	0.1	0.1
Contingent Purchase Price Liability – Current
Business Acquisition, Contingent Consideration [Line Items]
Contingent consideration, current	$ 600	$ 2,000
Contingent Purchase Price Liability – Non-current
Business Acquisition, Contingent Consideration [Line Items]
Contingent consideration, non-current	1,000	2,700
Acquisition of Client Lists
Business Acquisition, Contingent Consideration [Line Items]
Consideration paid in cash	200	500
Contingent consideration	$ 100	$ 300
Acquisition of Client Lists | Benefits and Insurance Services Practice Group
Business Acquisition, Contingent Consideration [Line Items]
Number of client list purchased | clientList	1	2
Previous Client List Purchases
Business Acquisition, Contingent Consideration [Line Items]
Consideration paid in cash	$ 100	$ 300