Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities:
Net income	$ 27,887	$ 19,899
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	2,707	2,528
Bad debt provision	650	1,350
Deferred income benefits	(1,305)	(2,405)
Stock-based compensation expense	1,196	1,144
Amortization of premium on marketable securities	303	346
Unrealized loss on marketable securities	0	82
Unrealized gain on deferred compensation fund investments	(759)	(937)
Changes in operating assets and liabilities:
Accounts and notes receivable	(26,812)	(7,891)
Prepaid income taxes	0	3,740
Inventories and supplies	27	(1,906)
Deferred compensation funding	(1,926)	(1,078)
Accounts payable and other accrued expenses	8,454	10,759
Accrued payroll, accrued and withheld payroll taxes	(1,989)	536
Accrued insurance claims	1,137	3,485
Deferred compensation liability	2,922	2,360
Income taxes payable	2,573	0
Prepaid expenses and other assets	(1,085)	(4,630)
Net cash provided by operating activities	13,980	27,382
Cash flows from investing activities:
Disposals of fixed assets	150	10
Additions to property and equipment	(1,702)	(1,825)
Purchases of marketable securities	(4,597)	(6,362)
Sales of marketable securities	3,450	15,784
Net cash (used in) provided by investing activities	(2,699)	7,607
Cash flows from financing activities:
Dividends paid	(22,931)	(21,803)
Reissuance of treasury stock pursuant to Dividend Reinvestment Plan	53	59
Tax benefit from equity compensation plans	1,128	1,051
Proceeds from the exercise of stock options	4,680	2,664
Net cash used in financing activities	(17,070)	(18,029)
Net (decrease) increase in cash and cash equivalents	(5,789)	16,960
Cash and cash equivalents at beginning of the period	68,949	38,639
Cash and cash equivalents at end of the period	63,160	55,599
Supplementary Cash Flow Information:
Income taxes cash payments, net of refunds	8,531	9,782
Issuance of Common Stock in 2013 and 2012, respectively, pursuant to Employee Stock Plans	$ 1,842	$ 1,250