CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 209,942	$ 149,922	$ 66,069
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of intangible assets	398	153	411
Depreciation expense	48,326	51,262	55,547
Stock-based compensation expense-restricted stock and stock units	41,464	50,906	56,949
Stock-based compensation expense-stock options			170
Excess tax benefits from stock-based compensation	(8,475)	(4,211)	(5,814)
Deferred income taxes	(14,993)	17,156	7,370
Provision for doubtful accounts receivable	7,133	6,673	6,795
Changes in assets and liabilities, net of effects of acquisitions:
Increase in accounts receivable	(21,354)	(81,314)	(68,008)
Increase in accounts payable, accrued expenses, accrued payroll costs and retirement obligations	16,672	64,932	41,626
Increase in income taxes payable	15,160	6,368	1,490
Change in other assets, net of change in other liabilities	(5,096)	(5,531)	13,278
Net cash flows provided by operating activities	289,177	256,316	175,883
CASH FLOWS FROM INVESTING ACTIVITIES:
Payment for acquisitions, net of cash acquired	(14,393)		(585)
Capital expenditures	(50,056)	(56,535)	(35,088)
Increase in trusts for employee benefits and retirement plans	(8,577)	(6,867)	(3,424)
Net cash flows used in investing activities	(73,026)	(63,402)	(39,097)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repurchases of common stock	(176,794)	(168,103)	(155,460)
Cash dividends paid	(84,129)	(80,303)	(76,591)
Decrease in notes payable and other indebtedness	(107)	(91)	(113)
Excess tax benefits from stock-based compensation	8,475	4,211	5,814
Proceeds from exercises of stock options	42,939	18,309	38,355
Net cash flows used in financing activities	(209,616)	(225,977)	(187,995)
Effect of exchange rate changes on cash and cash equivalents	1,764	(2,738)	552
Net increase (decrease) in cash and cash equivalents	8,299	(35,801)	(50,657)
Cash and cash equivalents at beginning of period	279,336	315,137	365,794
Cash and cash equivalents at end of period	287,635	279,336	315,137
Cash paid during the year for:
Interest	405	536	599
Income taxes, net of refunds	136,023	76,422	38,249
Non-cash items:
Stock repurchases awaiting settlement	$ 5,942	$ 2,466