Condensed Consolidated Statement Of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net income	$ 25,820	$ 29,943
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	39,323	27,174
Accretion and amortization of discount and premium of investments	0	331
Amortization of financing costs and discounts	2,853	2,370
Share-based compensation	3,614	2,809
Excess tax benefits from share-based compensation	0	(264)
Provision for doubtful accounts	2,640	2,825
Deferred income taxes	(2,361)	(3,101)
Loss on sale of available-for-sale investment	0	182
Decrease (increase) in:
Accounts receivable	25,110	15,773
Prepaid expenses and other current assets	(291)	370
Other assets	162	(715)
(Decrease) increase in:
Accounts payable and accrued expenses	(53,166)	(23,797)
Income taxes payable	4,795	6,360
Deferred revenue	2,384	1,250
Liability for uncertain tax positions	573	1,742
Other	(265)	1,272
Net cash provided by operating activities	51,191	64,524
Cash flows from investing activities:
Purchase of certificates of deposit	5	0
Sales of available-for-sale investments	0	26,224
Purchase of available-for-sale investments	0	(21,402)
Purchases of property and equipment	(9,660)	(4,321)
Acquisition of businesses, net of cash received	(3,563)	(47,989)
Purchases of intangible assets	(142)	(316)
Net Cash Provided by (Used in) Investing Activities	(13,370)	(47,804)
Cash flows from financing activities:
Proceeds from Lines of Credit	44,981	0
Repurchases of common stock and restricted stock	(314)	(1,786)
Issuance of common stock under employee stock purchase plan	67	58
Exercise of stock options	695	1,312
Dividends paid	(17,575)	(15,817)
Excess tax benefits from share-based compensation	0	264
Deferred payments for acquisitions	(2,299)	(14,386)
Proceeds from (Payments for) Other Financing Activities	(26)	(25)
Net Cash Provided by (Used in) Financing Activities	25,529	(30,380)
Effect of exchange rate changes on cash and cash equivalents	109	885
Cash and Cash Equivalents, Period Increase (Decrease)	63,459	(12,775)
Cash and cash equivalents	187,409	242,755
Cash and cash equivalents at end of period	$ 187,409	$ 242,755