Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 264,353	$ 221,875
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of intangible assets	0	557
Depreciation expense	39,487	36,170
Stock-based compensation expense—restricted stock and stock units	30,540	29,960
Excess tax benefits from stock-based compensation	(4,645)	(1,644)
Deferred income taxes	(6,912)	(11,167)
Provision for doubtful accounts	7,096	6,730
Changes in assets and liabilities:
Increase in accounts receivable	(96,505)	(123,259)
Increase in accounts payable, accrued expenses, accrued payroll and benefit costs	63,149	72,137
Increase in income taxes payable	34,854	36,991
Change in other assets, net of change in other liabilities	(11,176)	(10,530)
Net cash flows provided by operating activities	320,241	257,820
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(48,276)	(36,207)
Payments to trusts for employee deferred compensation plans	(19,578)	(18,220)
Net cash flows used in investing activities	(67,854)	(54,427)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repurchases of common stock	(201,209)	(124,679)
Cash dividends paid	(80,169)	(72,752)
Payments for notes payable and other indebtedness	(104)	(95)
Excess tax benefits from stock-based compensation	4,645	1,644
Proceeds from exercises of stock options	1,511	12,686
Net cash flows used in financing activities	(275,326)	(183,196)
Effect of exchange rate changes on cash and cash equivalents	(12,362)	(5,085)
Net (decrease) increase in cash and cash equivalents	(35,301)	15,112
Cash and cash equivalents at beginning of period	287,119	275,764
Cash and cash equivalents at end of period	251,818	290,876
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Stock repurchases awaiting settlement	$ 1,682	$ 2,152