Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenues:
Total revenues	$ 1,054,326	$ 955,166	$ 880,824
Cost of revenues:
Total cost of revenues	819,481	750,658	697,917
Gross margin	234,845	204,508	182,907
Selling, general and administrative expenses	169,642	155,259	141,916
Depreciation and amortization	6,228	5,326	4,844
Income from operations	58,975	43,923	36,147
Other income (expense):
Investment income, net	6,476	7,215	7,977
Interest expense	(141)	(372)	(1,244)
Other, net	(7)	(105)	(284)
Other income, net	6,328	6,738	6,449
Income before income taxes	65,303	50,661	42,596
Provision for income taxes	18,035	12,582	8,831
Net income	$ 47,268	$ 38,079	$ 33,765
Basic income per common share	$ 6.63	$ 5.05	$ 4.46
Weighted average number of basic common shares outstanding	7,130	7,540	7,577
Diluted income per common share	$ 6.54	$ 5.00	$ 4.39
Weighted average number of diluted common shares outstanding	7,226	7,621	7,688
Professional Employer Services [Member]
Revenues:
Total revenues	$ 937,363	$ 843,815	$ 777,430
Staffing Services [Member]
Revenues:
Total revenues	116,963	111,351	103,394
Direct Payroll Costs [Member]
Cost of revenues:
Total cost of revenues	87,944	83,821	78,380
Payroll Taxes and Benefits [Member]
Cost of revenues:
Total cost of revenues	522,392	469,888	418,793
Workers' Compensation [Member]
Cost of revenues:
Total cost of revenues	$ 209,145	$ 196,949	$ 200,744