Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 167,628	$ 136,691
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of intangible assets	0	557
Depreciation expense	26,568	24,063
Stock-based compensation expense—restricted stock and stock units	19,688	19,149
Excess tax benefits from stock-based compensation	(4,631)	(1,258)
Deferred income taxes	(986)	(3,143)
Provision for doubtful accounts	3,932	4,678
Changes in assets and liabilities:
Increase in accounts receivable	(44,033)	(68,662)
Increase in accounts payable, accrued expenses, accrued payroll and benefit costs	29,245	31,235
Increase in income taxes payable	41,667	31,205
Change in other assets, net of change in other liabilities	(12,683)	(10,376)
Net cash flows provided by operating activities	226,395	164,139
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(29,523)	(23,085)
Payments to trusts for employee deferred compensation plans	(13,013)	(9,806)
Net cash flows used in investing activities	(42,536)	(32,891)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repurchases of common stock	(104,220)	(65,158)
Cash dividends paid	(53,881)	(48,654)
Payments for notes payable and other indebtedness	(69)	(63)
Excess tax benefits from stock-based compensation	4,631	1,258
Proceeds from exercises of stock options	1,334	10,628
Net cash flows used in financing activities	(152,205)	(101,989)
Effect of exchange rate changes on cash and cash equivalents	(5,642)	2,755
Net increase in cash and cash equivalents	26,012	32,014
Cash and cash equivalents at beginning of period	287,119	275,764
Cash and cash equivalents at end of period	313,131	307,778
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Stock repurchases awaiting settlement	$ 16,826	$ 0