Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 175,032	$ 167,628
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of intangible assets	602	0
Depreciation expense	30,710	26,568
Stock-based compensation expense—restricted stock and stock units	22,093	19,688
Excess tax benefits from stock-based compensation	(802)	(4,631)
Deferred income taxes	(2,070)	(986)
Provision for doubtful accounts	3,213	3,932
Changes in assets and liabilities:
Increase in accounts receivable	(29,330)	(44,033)
Increase in accounts payable, accrued expenses, accrued payroll and benefit costs	7,215	29,245
Increase in income taxes payable	9,741	41,667
Change in other assets, net of change in other liabilities	(9,210)	(12,683)
Net cash flows provided by operating activities	207,194	226,395
CASH FLOWS FROM INVESTING ACTIVITIES:
Payments for acquisitions, net of cash acquired	(1,400)	0
Capital expenditures	(43,740)	(29,523)
Payments to trusts for employee deferred compensation plans	(11,251)	(13,013)
Net cash flows used in investing activities	(56,391)	(42,536)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repurchases of common stock	(81,544)	(104,220)
Cash dividends paid	(57,895)	(53,881)
Payments for notes payable and other indebtedness	(75)	(69)
Excess tax benefits from stock-based compensation	802	4,631
Proceeds from exercises of stock options	78	1,334
Net cash flows used in financing activities	(138,634)	(152,205)
Effect of exchange rate changes on cash and cash equivalents	1,968	(5,642)
Net increase in cash and cash equivalents	14,137	26,012
Cash and cash equivalents at beginning of period	224,577	287,119
Cash and cash equivalents at end of period	238,714	313,131
Non-cash items:
Stock repurchases awaiting settlement	$ 7,392	$ 16,826