Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 109,798	$ 96,167
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of intangible assets	342	463
Depreciation expense	15,652	16,253
Stock-based compensation expense—restricted stock and stock units	11,244	10,556
Deferred income taxes	5,736	1,695
Provision for doubtful accounts	2,325	1,778
Changes in assets and liabilities:
Increase in accounts receivable	(35,294)	(49,794)
Increase in accounts payable, accrued expenses, accrued payroll and benefit costs	1,398	13,527
Increase in income taxes payable	17,470	27,068
Change in other assets, net of change in other liabilities	(1,592)	(1,495)
Net cash flows provided by operating activities	127,079	116,218
CASH FLOWS FROM INVESTING ACTIVITIES:
Capital expenditures	(12,670)	(7,965)
Payments to trusts for employee deferred compensation plans	(10,410)	(10,585)
Net cash flows used in investing activities	(23,080)	(18,550)
CASH FLOWS FROM FINANCING ACTIVITIES:
Repurchases of common stock	(72,343)	(68,489)
Cash dividends paid	(37,887)	(34,919)
Payments for notes payable and other indebtedness	(49)	(44)
Net cash flows used in financing activities	(110,279)	(103,452)
Effect of exchange rate changes on cash and cash equivalents	(654)	3,018
Net decrease in cash and cash equivalents	(6,934)	(2,766)
Cash and cash equivalents at beginning of period	276,579	294,753
Cash and cash equivalents at end of period	269,645	291,987
Non-cash items:
Stock repurchases awaiting settlement	$ 7,332	$ 0