Condensed Consolidated Statement Of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flows from operating activities:
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 58,738	$ 59,727
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	18,241	10,197
Amortization of discount or premium of investments	820	581
Amortization of financing costs and discounts	300	0
Share-based compensation	4,683	4,425
Excess tax benefits from share-based compensation	(1,581)	(1,107)
Provision for doubtful accounts	1,279	2,601
Deferred income taxes	(542)	(3,307)
Decrease (increase) in:
Accounts receivable	2,886	(1,313)
Prepaid expenses and other current assets	929	(425)
Other assets	487	(257)
(Decrease) increase in:
Accounts payable and accrued expenses	4,998	(2,142)
Income taxes payable	212	11,903
Deferred revenue	14,049	822
Liability for uncertain tax positions	3,512	3,590
Other	10	29
Net cash provided by operating activities	109,021	85,324
Cash flows from investing activities:
Maturity of certificates of deposit	31,120	0
Purchase of certificates of deposit	(13,861)	(9,157)
Sales of available-for-sale investments	67,261	55,061
Purchase of available-for-sale investments	(91,729)	(28,242)
Purchases of property and equipment	(5,989)	(2,790)
Acquisition of businesses, net of cash received	(81,150)	(18,843)
Purchases of intangible assets	(1,261)	(2,745)
Net cash used in investing activities	(95,609)	(6,716)
Cash flows from financing activities:
Debt issuance costs	(47)	(77)
Repurchases of common stock and restricted stock	(2,266)	(60,224)
Issuance of common stock under employee stock purchase plan	106	61
Exercise of stock options	6,524	2,991
Dividends paid	(21,762)	(19,901)
Excess tax benefits from share-based compensation	1,581	1,107
Net cash used in financing activities	(15,864)	(76,043)
Effect of exchange rate changes on cash and cash equivalents	(1,302)	949
Net change in cash and cash equivalents	(3,754)	3,514
Cash and cash equivalents	214,926	142,873
Cash and cash equivalents at end of period	$ 214,926	$ 142,873