Segment Disclosures - Summary of Disaggregation of Revenue by Source (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Disaggregation of Revenue [Line Items]
Revenue	$ 361,952	$ 278,648	$ 753,674	$ 579,378
Financial Services
Disaggregation of Revenue [Line Items]
Revenue	259,308	186,589	548,054	390,738
Benefits and Insurance Services
Disaggregation of Revenue [Line Items]
Revenue	91,708	82,620	184,194	169,859
National Practices
Disaggregation of Revenue [Line Items]
Revenue	10,936	9,439	21,426	18,781
Accounting, tax, advisory and consulting
Disaggregation of Revenue [Line Items]
Revenue	259,308	186,589	548,054	390,738
Accounting, tax, advisory and consulting | Financial Services
Disaggregation of Revenue [Line Items]
Revenue	259,308	186,589	548,054	390,738
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	87,366	79,288	176,302	163,358
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	87,366	79,288	176,302	163,358
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	4,342	3,332	7,892	6,501
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	4,342	3,332	7,892	6,501
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	8,333	6,969	16,254	13,864
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	8,333	6,969	16,254	13,864
National practices consulting
Disaggregation of Revenue [Line Items]
Revenue	2,603	2,470	5,172	4,917
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	$ 2,603	$ 2,470	$ 5,172	$ 4,917