Consolidated Statements Of Cash Flows (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net income	$ 15,516us-gaap_NetIncomeLoss	$ 14,639us-gaap_NetIncomeLoss
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Depreciation and amortization	1,911	1,757
Bad debt provision	925us-gaap_ProvisionForDoubtfulAccounts	750us-gaap_ProvisionForDoubtfulAccounts
Deferred income tax benefits	525	3,075
Stock-based compensation expense	884us-gaap_ShareBasedCompensation	762us-gaap_ShareBasedCompensation
Amortization of premium on marketable securities	93	88
Unrealized gains on deferred compensation fund investments	(365)	(264)
Changes in operating assets and liabilities:
Accounts and notes receivable	(11,746)	(6,855)
Prepaid income taxes	912us-gaap_IncreaseDecreaseInPrepaidTaxes	(1,007)us-gaap_IncreaseDecreaseInPrepaidTaxes
Inventories and supplies	44us-gaap_IncreaseDecreaseInInventories	(309)us-gaap_IncreaseDecreaseInInventories
Prepaid expenses and other assets	(1,235)	(2,106)
Deferred compensation funding	451	(798)
Accounts payable and other accrued expenses	(2,351)	(469)
Accrued payroll, accrued and withheld payroll taxes	(21,002)	9,679
Accrued insurance claims	2,979	26
Deferred compensation liability	76	1,230
Income taxes payable	6,179	(1,878)
Net cash (used in) provided by operating activities	(6,204)	18,320
Cash flows from investing activities:
Disposals of fixed assets	41	60
Additions to property and equipment	(1,436)	(1,513)
Purchases of marketable securities	(989)	(1,228)
Sales of marketable securities	846	939
Net cash used in investing activities	(1,538)	(1,742)
Cash flows from financing activities:
Dividends paid	(12,655)us-gaap_PaymentsOfDividendsCommonStock	(12,077)us-gaap_PaymentsOfDividendsCommonStock
Reissuance of treasury stock pursuant to Dividend Reinvestment Plan	26	0
Tax benefit from equity compensation plans	499	477
Proceeds from the exercise of stock options	2,884	2,559
Net cash used in financing activities	(9,246)	(9,041)
Net change in cash and cash equivalents	(16,988)	7,537
Cash and cash equivalents at beginning of the period	75,280	64,155
Cash and cash equivalents at end of the period	58,292	71,692
Supplementary Cash Flow Information:
Cash paid for interest	22us-gaap_InterestPaid	13us-gaap_InterestPaid
Cash paid for income taxes, net of refunds	1,424us-gaap_IncomeTaxesPaidNet	7,821us-gaap_IncomeTaxesPaidNet
Issuance of Common Stock in 2015 and 2014, respectively, pursuant to Employee Stock Purchase Plan	$ 1,701	$ 1,851

The component of income tax expense for the period representing the increase (decrease) in the entity's deferred tax assets and liabilities pertaining to continuing operations, less the amount attributable to the tax benefit from deferred compensation plan.

No definition available.