Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 136,691	$ 118,952
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of intangible assets	557	867
Depreciation expense	24,063	23,326
Stock-based compensation expense-restricted stock and stock units	19,149	17,976
Excess tax benefits from stock-based compensation	(1,258)	(1,280)
Deferred income taxes	(3,143)	(13,286)
Provision for doubtful accounts	4,678	3,063
Changes in assets and liabilities:
Increase in accounts receivable	(68,662)	(54,751)
Increase in accounts payable, accrued expenses, accrued payroll costs and retirement obligations	31,235	23,734
Increase in income taxes payable	31,205	15,265
Change in other assets, net of change in other liabilities	(10,376)	(3,931)
Net cash flows provided by operating activities	164,139	129,935
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(23,085)	(19,104)
Increase in trusts for employee benefits and retirement plans	(9,806)	(33,076)
Net cash flows used in investing activities	(32,891)	(52,180)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repurchases of common stock	(65,158)	(86,381)
Cash dividends paid	(48,654)	(43,886)
Decrease in notes payable and other indebtedness	(63)	(4,388)
Excess tax benefits from stock-based compensation	1,258	1,280
Proceeds from exercises of stock options	10,628	22,396
Net cash flows used in financing activities	(101,989)	(110,979)
Effect of exchange rate changes on cash and cash equivalents	2,755	(7,440)
Net increase (decrease) in cash and cash equivalents	32,014	(40,664)
Cash and cash equivalents at beginning of period	275,764	287,635
Cash and cash equivalents at end of period	$ 307,778	$ 246,971