Basis of Presentation of Interim Period Statements - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2019 USD ($) Company	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Organization Consolidation And Presentation Of Financial Statements [Abstract]
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
Allowance for doubtful accounts	$ 586,000		$ 533,000
Estimate of liability for unpaid safety incentives	27,300,000		29,200,000
One-time customer Incentive	7,200,000		$ 9,800,000
Interest paid		$ 1,800,000
Income taxes paid	$ 5,000,000	$ 100,000