Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 221,875	$ 185,310
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of intangible assets	557	1,300
Depreciation expense	36,170	34,995
Stock-based compensation expense—restricted stock and stock units	29,960	28,559
Excess tax benefits from stock-based compensation	(1,644)	(1,564)
Deferred income taxes	(11,167)	(23,540)
Provision for doubtful accounts	6,730	6,173
Changes in assets and liabilities:
Increase in accounts receivable	(123,259)	(61,039)
Increase in accounts payable, accrued expenses, accrued payroll costs and retirement obligations	72,137	27,842
Increase in income taxes payable	36,991	11,015
Change in other assets, net of change in other liabilities	(10,530)	2,006
Net cash flows provided by operating activities	257,820	211,057
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(36,207)	(32,117)
Payments to trusts for employee benefits and retirement plans	(18,220)	(38,479)
Net cash flows used in investing activities	(54,427)	(70,596)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repurchases of common stock	(124,679)	(106,782)
Cash dividends paid	(72,752)	(65,612)
Decrease in notes payable and other indebtedness	(95)	(4,430)
Excess tax benefits from stock-based compensation	1,644	1,564
Proceeds from exercises of stock options	12,686	29,895
Net cash flows used in financing activities	(183,196)	(145,365)
Effect of exchange rate changes on cash and cash equivalents	(5,085)	(2,984)
Net increase (decrease) in cash and cash equivalents	15,112	(7,888)
Cash and cash equivalents at beginning of period	275,764	287,635
Cash and cash equivalents at end of period	290,876	279,747
Stock Repurchases Awaiting Settlement	$ 2,152	$ 12,178