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	$ 28,560	$ 27,887
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	3,581	2,707
Bad debt provision	1,550	650
Deferred income taxes (benefits)	1,486	(1,305)
Stock-based compensation expense	1,531	1,196
Amortization of premium on marketable securities	174	303
Unrealized gain on deferred compensation fund investments	(888)	(759)
Changes in operating assets and liabilities:
Accounts and notes receivable	(16,695)	(26,812)
Inventories and supplies	(472)	27
Prepaid expenses and other assets	(4,191)	(1,085)
Deferred compensation funding	(1,803)	(1,926)
Accounts payable and other accrued expenses	(1,942)	8,454
Accrued payroll, accrued and withheld payroll taxes	(3,338)	(1,989)
Accrued insurance claims	740	1,137
Deferred compensation liability	3,031	2,922
Income taxes payable	3,503	2,573
Net cash provided by operating activities	14,827	13,980
Cash flows from investing activities:
Disposals of fixed assets	363	150
Additions to property and equipment	(2,738)	(1,702)
Purchases of marketable securities	(1,937)	(4,597)
Sales of marketable securities	2,115	3,450
Net cash used in investing activities	(2,197)	(2,699)
Cash flows from financing activities:
Dividends paid	(24,263)	(22,931)
Reissuance of treasury stock pursuant to Dividend Reinvestment Plan	28	53
Tax benefit from equity compensation plans	885	1,128
Proceeds from the exercise of stock options	3,834	4,680
Net cash used in financing activities	(19,516)	(17,070)
Net change in cash and cash equivalents	(6,886)	(5,789)
Cash and cash equivalents at beginning of the period	64,155	68,949
Cash and cash equivalents at end of the period	57,269	63,160
Supplementary Cash Flow Information:
Cash paid for interest	73	0
Cash paid for income taxes, net of refunds	10,737	8,531
Issuance of Common Stock in 2014 and 2013, respectively, pursuant to Employee Stock Purchase Plan	$ 1,851	$ 1,842