Condensed Consolidated Statement Of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 29,943	$ 21,877
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	27,174	21,287
Amortization of discount or premium of investments	331	273
Amortization of financing costs and discounts	2,370	2,222
Share-based compensation	2,809	3,004
Excess tax benefits from share-based compensation	(264)	(334)
Provision for doubtful accounts	2,825	1,610
Deferred income taxes	(3,101)	(494)
Loss on disposal of fixed assets	12	0
(Gain) loss on sale of available-for-sale investments	182	(24)
Decrease (increase) in:
Accounts receivable	15,773	9,254
Prepaid expenses and other current assets	370	(4)
Other assets	(727)	25
(Decrease) increase in:
Accounts payable and accrued expenses	(23,797)	(12,902)
Income taxes payable	6,360	(1,283)
Deferred revenue	1,250	(1,340)
Liability for uncertain tax positions	1,742	2,595
Other	1,272	(50)
Net cash provided by operating activities	64,524	45,716
Cash flows from investing activities:
Sales of available-for-sale investments	26,224	28,994
Purchase of available-for-sale investments	(21,402)	(19,819)
Purchases of property and equipment	(4,321)	(2,956)
Acquisition of businesses, net of cash received	(47,989)	(72,215)
Purchases of intangible assets	(316)	(327)
Net cash used in investing activities	(47,804)	(66,323)
Cash flows from financing activities:
Repurchases of common stock and restricted stock	(1,786)	(705)
Issuance of common stock under employee stock purchase plan	58	61
Exercise of stock options	1,312	65
Dividends paid	(15,817)	(14,110)
Excess tax benefits from share-based compensation	264	334
Deferred payments for acquisitions	(14,386)	(2,356)
Proceeds from (Payments for) Other Financing Activities	(25)	(50)
Net cash used in financing activities	(30,380)	(16,761)
Effect of exchange rate changes on cash and cash equivalents	885	(4,278)
Net change in cash and cash equivalents	(12,775)	(41,646)
Cash and cash equivalents	242,755	392,017
Cash and cash equivalents at end of period	$ 242,755	$ 392,017