Condensed Consolidated Statement Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flows from operating activities:
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 22,771	$ 28,539
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	8,762	4,926
Amortization of discount or premium of investments	453	319
Amortization of financing costs and discounts	150	0
Share-based compensation	2,348	2,280
Excess tax benefits from share-based compensation	(280)	(286)
Provision for doubtful accounts	833	1,289
Deferred income taxes	(1,446)	(3,498)
Decrease (increase) in:
Accounts receivable	2,495	936
Prepaid expenses and other current assets	(139)	(1,055)
Other assets	357	150
(Decrease) increase in:
Accounts payable and accrued expenses	160	(4,488)
Income taxes payable	2,138	7,532
Deferred revenue	92	700
Liability for uncertain tax positions	1,294	1,536
Other	60	62
Net cash provided by operating activities	40,048	38,942
Cash flows from investing activities:
Maturity of certificates of deposit	22,106	0
Purchase of certificates of deposit	(8,165)	(5,822)
Sales of available-for-sale investments	31,932	45,164
Purchase of available-for-sale investments	(35,244)	(15,537)
Purchases of property and equipment	(1,933)	(1,159)
Acquisition of businesses, net of cash received	(62,771)	(18,843)
Purchases of intangible assets	(333)	(900)
Net cash used in investing activities	(54,408)	2,903
Cash flows from financing activities:
Debt issuance costs	(47)	0
Repurchases of common stock and restricted stock	(2,069)	(40,273)
Issuance of common stock under employee stock purchase plan	56	29
Exercise of stock options	2,025	2,591
Dividends paid	(10,684)	(9,975)
Excess tax benefits from share-based compensation	280	286
Net cash provided by financing activities	(10,439)	(47,342)
Effect of exchange rate changes on cash and cash equivalents	(755)	1,820
Net change in cash and cash equivalents	(25,554)	(3,677)
Cash and cash equivalents	193,126	135,682
Cash and cash equivalents at end of period	$ 193,126	$ 135,682