Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities:
Net income	$ 47,129	$ 44,214	$ 38,156
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	6,204	5,116	4,387
Bad debt provision	1,990	2,160	2,450
Deferred income (benefits) tax	(4,922)	(3,493)	275
Stock-based compensation expense	2,607	2,538	2,152
Amortization of premium on marketable securities	537	654	999
Unrealized loss on marketable securities	0	82	486
Unrealized (gain) loss on deferred compensation fund investments	(2,820)	(1,871)	104
Changes in operating assets and liabilities:
Accounts and notes receivable	(50,879)	(11,634)	(24,769)
Prepaid income taxes	0	405	3,574
Inventories and supplies	(3,772)	(3,531)	(4,531)
Notes receivable — long term	(3,956)	(340)	3,572
Deferred compensation funding	(4,369)	(4,051)	(1,804)
Accounts payable and other accrued expenses	25,961	13,664	(1,079)
Accrued payroll, accrued and withheld payroll taxes	6,349	6,142	6,319
Accrued insurance claims	3,616	4,908	732
Deferred compensation liability	7,721	6,337	2,145
Income taxes payable	(28)	1,906	0
Prepaid expenses and other assets	790	(2,830)	(220)
Net cash provided by operating activities	32,158	60,376	32,948
Cash flows from investing activities:
Disposals of fixed assets	158	26	22
Additions to property and equipment	(3,762)	(3,484)	(5,545)
Purchases of marketable securities	(6,598)	(10,833)	(18,934)
Sales of marketable securities	15,807	19,978	29,971
Cash paid for acquisition	(5,000)	0	(1,000)
Net cash provided by investing activities	605	5,687	4,514
Cash flows from financing activities:
Dividends paid	(46,707)	(44,093)	(42,228)
Reissuance of treasury stock pursuant to Dividend Reinvestment Plan	107	118	128
Tax benefit from equity compensation plans	2,615	2,649	1,222
Proceeds from the exercise of stock options	6,428	5,573	2,363
Net cash used in financing activities	(37,557)	(35,753)	(38,515)
Net change in cash and cash equivalents	(4,794)	30,310	(1,053)
Cash and cash equivalents at beginning of the period	68,949	38,639	39,692
Cash and cash equivalents at end of the period	64,155	68,949	38,639
Supplementary Cash Flow Information:
Cash paid for interest	4	3	2
Cash paid for interest	$ 21,694	$ 24,681	$ 14,614