Revenue - Summary of Disaggregation of Revenue by Source (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Total revenue	$ 1,411,979	$ 1,104,925	$ 963,897
Financial Services
Disaggregation of Revenue [Line Items]
Total revenue	1,010,068	734,026	629,778
Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Total revenue	358,007	332,323	297,758
National Practices
Disaggregation of Revenue [Line Items]
Total revenue	43,904	38,576	36,361
Accounting, tax, advisory and consulting
Disaggregation of Revenue [Line Items]
Total revenue	1,010,068	734,026	629,778
Accounting, tax, advisory and consulting | Financial Services
Disaggregation of Revenue [Line Items]
Total revenue	1,010,068	734,026	629,778
Core Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Total revenue	342,063	319,684	286,361
Core Benefits and Insurance Services | Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Total revenue	342,063	319,684	286,361
Non-core Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Total revenue	15,944	12,639	11,397
Non-core Benefits and Insurance Services | Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Total revenue	15,944	12,639	11,397
Managed networking, hardware services
Disaggregation of Revenue [Line Items]
Total revenue	33,503	28,456	26,458
Managed networking, hardware services | National Practices
Disaggregation of Revenue [Line Items]
Total revenue	33,503	28,456	26,458
National Practices consulting
Disaggregation of Revenue [Line Items]
Total revenue	10,401	10,120	9,903
National Practices consulting | National Practices
Disaggregation of Revenue [Line Items]
Total revenue	$ 10,401	$ 10,120	$ 9,903