Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net income	$ 14,954	$ 8,578
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization	1,352	1,248
Bad debt provision	450	750
Deferred income tax (benefits)	305	(1,001)
Stock-based compensation expense	583	560
Amortization of premium on marketable securities	154	198
Unrealized loss on marketable securities	0	56
Unrealized gain on deferred compensation fund investments	(789)	(1,297)
Changes in operating assets and liabilities:
Accounts and notes receivable	(10,695)	(831)
Prepaid income taxes	(1,628)	405
Inventories and supplies	79	(822)
Deferred compensation funding	(1,423)	(464)
Accounts payable and other accrued expenses	7,670	11,338
Accrued payroll, accrued and withheld payroll taxes	(15,282)	(12,516)
Accrued insurance claims	19	1,601
Deferred compensation liability	2,312	1,952
Income taxes payable	(1,906)	2,655
Prepaid expenses and other assets	(1,182)	(2,969)
Net cash (used in) provided by operating activities	(5,027)	9,441
Cash flows from investing activities:
Disposals of fixed assets	164	0
Additions to property and equipment	(968)	(813)
Purchases of marketable securities	(1,537)	(1,223)
Sales of marketable securities	185	10,895
Net cash (used in) provided by investing activities	(2,156)	8,859
Cash flows from financing activities:
Dividends paid	(11,415)	(10,847)
Reissuance of treasury stock pursuant to Dividend Reinvestment Plan	27	30
Tax benefit from equity compensation plans	709	294
Proceeds from the exercise of stock options	3,640	1,840
Net cash used in financing activities	(7,039)	(8,683)
Net (decrease) increase in cash and cash equivalents	(14,222)	9,617
Cash and cash equivalents at beginning of the period	68,949	38,639
Cash and cash equivalents at end of the period	54,727	48,256
Supplementary Cash Flow Information:
Income taxes cash payments, net of refunds	6,523	2,852
Issuance of Common Stock in 2013 and 2012, respectively, pursuant to Employee Stock Plans	$ 1,842	$ 1,250