Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 21,206	$ 14,684
Reconciliations of net income to net cash provided by operating activities:
Depreciation and amortization	3,228	2,989
Losses (gains) recognized on investments	36	(76)
Share-based compensation	3,992	3,064
Changes in certain operating assets and liabilities:
Trade accounts receivable	(25,910)	(29,884)
Income taxes receivable	1,686
Prepaid expenses and other	(6,720)	(2,706)
Accounts payable	(702)	(911)
Accrued payroll, payroll taxes and related benefits	13,079	29,157
Other accrued liabilities	(772)	(267)
Income taxes payable	2,429	3,740
Workers' compensation claims liabilities	35,391	38,163
Safety incentives liability	68	2,724
Customer deposits, long-term liabilities and other assets, net	(109)	(150)
Net cash provided by operating activities	46,902	60,527
Cash flows from investing activities:
Purchase of property and equipment	(4,442)	(2,612)
Purchase of investments	(1,688)	(3,559)
Proceeds from sales and maturities of investments	1,481	7,889
Purchase of restricted investments	(103,861)	(363,680)
Proceeds from sales and maturities of restricted investments	54,819	53,039
Net cash used in investing activities	(53,691)	(308,923)
Cash flows from financing activities:
Proceeds from credit-line borrowings	8,500	24,899
Payments on credit-line borrowings	(8,500)	(24,899)
Payments on long-term debt	(165)	(166)
Common stock repurchased on vesting of restricted stock units	(2,952)	(1,666)
Dividends paid	(5,499)	(5,449)
Proceeds from exercise of stock options and vesting of restricted stock units	324	148
Net cash used in financing activities	(8,292)	(7,133)
Net decrease in cash, cash equivalents and restricted cash	(15,081)	(255,529)
Cash, cash equivalents and restricted cash, beginning of period	120,205	341,330
Cash, cash equivalents and restricted cash, end of period	$ 105,124	$ 85,801