Summary of Operations and Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2025 USD ($) Segment Company Market $ / shares shares	Dec. 31, 2024 USD ($) $ / shares shares	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Basis Of Presentation Of Interim Period Statements [Line Items]
Number of markets | Market	69
Common stock, shares authorized | shares	82,000,000	82,000,000
Common stock, par value | $ / shares	$ 0.01	$ 0.01
Number of operating segment | Segment	1
Segment Reporting, CODM, Individual Title and Position or Group Name [Extensible Enumeration]	srt:ChiefExecutiveOfficerMember
Revenue recognition professional employer service contracts term	1 year
Professional employer service contract cancellation and termination period	30 days
Payment term for staffing customers	30 days
Number of wholly-owned insurance companies | Company	2
Cash and cash equivalents, maturity term	3 months
Interest income	$ 8,700,000	$ 10,900,000	$ 9,100,000
Payroll weekly payment term	30 days
Unbilled receivables	$ 241,500,000	218,800,000
Remaining trade accounts receivable	7,500,000	16,600,000
Allowance for expected credit losses	350,000	885,000	885,000	$ 893,000
Goodwill and intangible assets impairment	0
Impairment of long lived asset	0
Income taxes paid net of income tax refunds received	15,400,000	13,700,000	22,200,000
Federal income taxes paid, net of income tax refunds received	12,500,000	13,100,000	16,600,000
State income taxes paid, net of income tax refunds received	2,900,000	$ 600,000	5,600,000
Threshold percentage of income tax paid		5.00%
Maximum additional premiums charged amount for twelve month policy period, if claims develop adversely	0
2021-2022 Policy [Member]
Basis Of Presentation Of Interim Period Statements [Line Items]
Maximum additional premiums charged amount for twelve month policy period, if claims develop adversely	7,500,000
2023-2024 Policy [Member]
Basis Of Presentation Of Interim Period Statements [Line Items]
Maximum additional premiums charged amount for twelve month policy period, if claims develop adversely	$ 0
Minimum [Member]
Basis Of Presentation Of Interim Period Statements [Line Items]
Likelihood of tax benefit being realized upon settlement	50.00%
Minimum [Member] | 2021-2022 Policy [Member]
Basis Of Presentation Of Interim Period Statements [Line Items]
Maximum savings amount for twelve month policy period, if claims develop favorably	$ 20,000,000
Minimum [Member] | 2022-2023 Policy [Member]
Basis Of Presentation Of Interim Period Statements [Line Items]
Maximum savings amount for twelve month policy period, if claims develop favorably	20,000,000
Minimum [Member] | 2023-2024 Policy [Member]
Basis Of Presentation Of Interim Period Statements [Line Items]
Maximum savings amount for twelve month policy period, if claims develop favorably	20,000,000
Minimum [Member] | 2024-2025 Policy [Member]
Basis Of Presentation Of Interim Period Statements [Line Items]
Maximum savings amount for twelve month policy period, if claims develop favorably	20,000,000
Maximum [Member] | 2021-2022 Policy [Member]
Basis Of Presentation Of Interim Period Statements [Line Items]
Maximum savings amount for twelve month policy period, if claims develop favorably	30,000,000
Maximum [Member] | 2022-2023 Policy [Member]
Basis Of Presentation Of Interim Period Statements [Line Items]
Maximum savings amount for twelve month policy period, if claims develop favorably	30,000,000
Maximum [Member] | 2023-2024 Policy [Member]
Basis Of Presentation Of Interim Period Statements [Line Items]
Maximum savings amount for twelve month policy period, if claims develop favorably	30,000,000
Maximum [Member] | 2024-2025 Policy [Member]
Basis Of Presentation Of Interim Period Statements [Line Items]
Maximum savings amount for twelve month policy period, if claims develop favorably	30,000,000
California [Member]
Basis Of Presentation Of Interim Period Statements [Line Items]
State income taxes paid, net of income tax refunds received	$ 2,300,000		$ 4,000,000
California [Member] | Revenue [Member] | Geographic Concentration Risk [Member]
Basis Of Presentation Of Interim Period Statements [Line Items]
Percentage of revenue attributable to geographic area	72.00%	72.00%	72.00%