Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Cash flows from operating activities:
Net income	$ 3,700	$ 3,337
Reconciliations of net income to net cash provided by operating activities:
Depreciation and amortization	1,197	966
Losses (gains) recognized on marketable securities	1	(1)
Gain recognized on sale and leaseback	0	(61)
Deferred income taxes	(425)	(58)
Share-based compensation	671	367
Excess tax benefit from share-based compensation	(124)	(1,187)
Changes in certain assets and liabilities:
Trade accounts receivable, net	(18,422)	(16,931)
Income taxes receivable	0	(5,358)
Prepaid expenses and other	(2,257)	1,869
Accounts payable	(817)	815
Accrued payroll, payroll taxes and related benefits	13,194	17,267
Other accrued liabilities	768	330
Income taxes payable	1,210	915
Workers' compensation claims liabilities	10,062	13,979
Safety incentives liability	(368)	1,097
Customer deposits, long-term liabilities and other assets, net	291	84
Net cash provided by operating activities	8,681	17,430
Cash flows from investing activities:
Purchase of property and equipment	(2,434)	(2,410)
Proceeds from sales and maturities of marketable securities	7,045	57,773
Purchase of marketable securities	(23,989)	(40,881)
Purchase of restricted certificates of deposit	(8,154)	(63,944)
Proceeds from maturities of restricted marketable securities	4,017	4,815
Purchase of restricted marketable securities	(27,508)	(5,594)
Net cash used in investing activities	(51,023)	(50,241)
Cash flows from financing activities:
Proceeds from credit-line borrowings	3,731	132,664
Payments on credit-line borrowings	(3,731)	(137,196)
Payments on long-term debt	(110)	(110)
Repurchase of common stock	(991)	0
Dividends paid	(2,582)	(1,834)
Proceeds from exercise of stock options	213	1,200
Excess tax benefits from share-based compensation	124	1,187
Net cash used in financing activities	(3,346)	(4,089)
Net decrease in cash and cash equivalents	(45,688)	(36,900)
Cash and cash equivalents, beginning of period	93,557	45,747
Cash and cash equivalents, end of period	$ 47,869	$ 8,847