Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income (loss)	$ 18,799	$ 25,494	$ (25,546)
Reconciliations of net income (loss) to net cash provided by operating activities:
Depreciation and amortization	3,253	2,851	2,506
(Gains) losses recognized on investments	(3)	(2)	3
Loss recognized on sale of property	31
Deferred income taxes	(1,704)	2,728	(9,792)
Share-based compensation	2,782	2,386	1,699
Excess tax from share-based compensation	(253)	68	(578)
Changes in certain assets and liabilities:
Trade accounts receivable, net	(35,955)	12,097	(17,041)
Income taxes receivable	1,038	10,521	(11,421)
Prepaid expenses and other	(726)	640	(387)
Accounts payable	1,727	498	(533)
Accrued payroll, payroll taxes and related benefits	31,767	5,506	21,950
Other accrued liabilities	1,508	(64)	3,893
Income taxes payable	3,294	506	411
Workers' compensation claims liabilities	51,235	30,397	104,223
Safety incentives liability	3,582	7,021	1,146
Customer deposits, long-term liabilities and other assets, net	(68)	(16)	(937)
Net cash provided by operating activities	80,307	100,631	69,596
Cash flows from investing activities:
Purchase of equipment and software	(7,106)	(2,996)	(4,632)
Proceeds from sale of property	1,459
Purchase of investments	(264)	(8,214)	(38,434)
Proceeds from sales and maturities of investments	4,796	52,996	13,241
Purchase of restricted cash and investments	(185,845)	(336,083)	(163,174)
Proceeds from sales and maturities of restricted cash and investments	153,890	238,701	10,524
Net cash used in investing activities	(33,070)	(55,596)	(182,475)
Cash flows from financing activities:
Proceeds from credit-line borrowings	14,868	46,106	6,242
Payments on credit-line borrowings	(14,868)	(46,106)	(6,242)
Proceeds from the issuance of long-term debt			40,000
Commitment fee from the issuance of long-term debt			(400)
Payments on long-term debt	(15,220)	(25,220)	(220)
Repurchase of common stock			(3,676)
Common stock repurchased on vesting of restricted stock units	(433)	(465)	(407)
Dividends paid	(6,359)	(6,310)	(5,443)
Proceeds from the exercise of stock options	72	702	434
Excess tax benefit from share-based compensation	253	(68)	578
Net cash (used in) provided by financing activities	(21,687)	(31,361)	30,866
Net increase (decrease) in cash and cash equivalents	25,550	13,674	(82,013)
Cash and cash equivalents, beginning of year	25,218	11,544	93,557
Cash and cash equivalents, end of year	$ 50,768	$ 25,218	$ 11,544