Segment Disclosures - Summary of Disaggregation of Revenue by Source (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Disaggregation of Revenue [Line Items]
Revenue	$ 391,722	$ 300,730
Financial Services
Disaggregation of Revenue [Line Items]
Revenue	288,746	204,149
Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Revenue	92,486	87,239
National Practices
Disaggregation of Revenue [Line Items]
Revenue	10,490	9,342
Accounting, tax, advisory and consulting
Disaggregation of Revenue [Line Items]
Revenue	288,746	204,149
Accounting, tax, advisory and consulting | Financial Services
Disaggregation of Revenue [Line Items]
Revenue	288,746	204,149
Accounting, tax, advisory and consulting | Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Revenue	0	0
Accounting, tax, advisory and consulting | National Practices
Disaggregation of Revenue [Line Items]
Revenue	0	0
Core benefits and insurance services
Disaggregation of Revenue [Line Items]
Revenue	88,936	84,070
Core benefits and insurance services | Financial Services
Disaggregation of Revenue [Line Items]
Revenue	0	0
Core benefits and insurance services | Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Revenue	88,936	84,070
Core benefits and insurance services | National Practices
Disaggregation of Revenue [Line Items]
Revenue	0	0
Non-core benefits and insurance services
Disaggregation of Revenue [Line Items]
Revenue	3,550	3,169
Non-core benefits and insurance services | Financial Services
Disaggregation of Revenue [Line Items]
Revenue	0	0
Non-core benefits and insurance services | Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Revenue	3,550	3,169
Non-core benefits and insurance services | National Practices
Disaggregation of Revenue [Line Items]
Revenue	0	0
Managed networking, hardware services
Disaggregation of Revenue [Line Items]
Revenue	7,921	6,895
Managed networking, hardware services | Financial Services
Disaggregation of Revenue [Line Items]
Revenue	0	0
Managed networking, hardware services | Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Revenue	0	0
Managed networking, hardware services | National Practices
Disaggregation of Revenue [Line Items]
Revenue	7,921	6,895
National practices consulting
Disaggregation of Revenue [Line Items]
Revenue	2,569	2,447
National practices consulting | Financial Services
Disaggregation of Revenue [Line Items]
Revenue	0	0
National practices consulting | Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Revenue	0	0
National practices consulting | National Practices
Disaggregation of Revenue [Line Items]
Revenue	$ 2,569	$ 2,447