Segment Disclosures - Summary of Disaggregation of Revenue by Source (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Disaggregation of Revenue [Line Items]
Revenue	$ 410,539	$ 363,262	$ 1,263,647	$ 1,116,936
Financial Services
Disaggregation of Revenue [Line Items]
Revenue	298,372	259,998	932,388	808,052
Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Revenue	100,287	92,067	296,179	276,261
National Practices
Disaggregation of Revenue [Line Items]
Revenue	11,880	11,197	35,080	32,623
Accounting, tax, advisory and consulting
Disaggregation of Revenue [Line Items]
Revenue	298,372	259,998	932,388	808,052
Accounting, tax, advisory and consulting | Financial Services
Disaggregation of Revenue [Line Items]
Revenue	298,372	259,998	932,388	808,052
Accounting, tax, advisory and consulting | Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Accounting, tax, advisory and consulting | National Practices
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Core benefits and insurance services
Disaggregation of Revenue [Line Items]
Revenue	95,951	88,364	283,599	264,666
Core benefits and insurance services | Financial Services
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Core benefits and insurance services | Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Revenue	95,951	88,364	283,599	264,666
Core benefits and insurance services | National Practices
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Non-core benefits and insurance services
Disaggregation of Revenue [Line Items]
Revenue	4,336	3,703	12,580	11,595
Non-core benefits and insurance services | Financial Services
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Non-core benefits and insurance services | Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Revenue	4,336	3,703	12,580	11,595
Non-core benefits and insurance services | National Practices
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Managed networking, hardware services
Disaggregation of Revenue [Line Items]
Revenue	9,205	8,514	27,226	24,768
Managed networking, hardware services | Financial Services
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Managed networking, hardware services | Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
Managed networking, hardware services | National Practices
Disaggregation of Revenue [Line Items]
Revenue	9,205	8,514	27,226	24,768
National practices consulting
Disaggregation of Revenue [Line Items]
Revenue	2,675	2,683	7,854	7,855
National practices consulting | Financial Services
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
National practices consulting | Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Revenue	0	0	0	0
National practices consulting | National Practices
Disaggregation of Revenue [Line Items]
Revenue	$ 2,675	$ 2,683	$ 7,854	$ 7,855