Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net income	$ 11,607	$ 2,117
Reconciliations of net income to net cash provided by operating activities:
Depreciation and amortization	1,939	2,278
Non-cash lease expense	3,509
Losses recognized on investments	26	38
Share-based compensation	3,828	2,583
Changes in certain operating assets and liabilities:
Trade accounts receivable	(11,631)	(15,896)
Income taxes receivable		(643)
Prepaid expenses and other	(1,840)	(4,100)
Accounts payable	488	(1,215)
Accrued payroll, payroll taxes and related benefits	24,740	4,533
Other accrued liabilities	(4,658)	(80)
Income taxes payable	(1,733)
Workers' compensation claims liabilities	17,470	27,341
Safety incentives liability	(1,894)	(468)
Operating lease liabilities	(3,032)
Other assets and liabilities, net	46	(27)
Net cash provided by operating activities	38,865	16,461
Cash flows from investing activities:
Purchase of property and equipment	(5,127)	(3,517)
Purchase of investments	(117)	(1,401)
Proceeds from sales and maturities of investments	15,262	1,369
Purchase of restricted investments	(3,245)	(103,388)
Proceeds from sales and maturities of restricted investments	34,765	32,749
Net cash provided by (used in) investing activities	41,538	(74,188)
Cash flows from financing activities:
Proceeds from credit-line borrowings	18,843	8,500
Payments on credit-line borrowings	(18,843)	(8,500)
Payments on long-term debt	(111)	(110)
Common stock repurchased on vesting of restricted stock units	(178)	(168)
Dividends paid	(3,705)	(3,653)
Proceeds from exercise of stock options	178	101
Net cash used in financing activities	(3,816)	(3,830)
Net increase (decrease) in cash, cash equivalents and restricted cash	76,587	(61,557)
Cash, cash equivalents and restricted cash, beginning of period	140,702	120,205
Cash, cash equivalents and restricted cash, end of period	$ 217,289	$ 58,648