Consolidated Statement Of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Cash flows from operating activities:
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 121,663	$ 114,766	$ 83,047
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	22,164	19,756	14,510
Amortization of discount or premium of investments	(1,603)	(941)	(837)
Amortization of financing costs and discounts	249	0	0
Share-based compensation	9,132	8,968	10,937
Excess tax benefits from share-based compensation	961	13,561	62
Provision for doubtful accounts	4,289	6,900	1,965
Deferred income taxes	1,150	6,822	(541)
Loss on disposal of fixed assets	54	117	64
(Gain) loss on available-for-sale investments	(266)	(552)	(4,477)
Decrease (increase) in:
Accounts receivable	5,417	9,509	246
Prepaid expenses and other current assets	2,028	(4,261)	2,253
Other assets	243	(204)	162
(Decrease) increase in:
Accounts payable and accrued expenses	5,138	847	1,318
Income taxes payable	4,139	9,679	(15,767)
Deferred revenue	1,612	8,664	(1,592)
Liability for uncertain tax positions	7,601	(7,786)	8,114
Other	32	231	693
Net cash provided by operating activities	169,911	150,748	96,385
Cash flows from investing activities:
Maturity of certificates of deposit	8,000	0	31,653
Purchase of certificates of deposit	(34,673)	(8,000)	0
Sales of available-for-sale investments	138,709	29,777	48,843
Purchase of available-for-sale investments	(151,989)	(82,879)	(52,921)
Purchases of property and equipment	(5,061)	(6,844)	(1,842)
Proceeds from sale of assets	156	4	13
Acquisition of businesses, net of cash received	(198,341)	(3,926)	(248,568)
Purchases of intangible assets	(6,295)	(4,312)	(8,312)
Net cash used in investing activities	(249,494)	(76,180)	(231,134)
Cash flows from financing activities:
Issuance of long-term debt	245,000	0	0
Debt issuance costs	(1,384)	0	0
Repurchases of common stock and restricted stock	(60,282)	(1,281)	(4,221)
Issuance of common stock under employee stock purchase plan	157	142	109
Exercise of stock options	5,646	7,090	6,721
Proceeds from noncontrolling interests	8,557	0	0
Dividends paid	(40,263)	(19,174)	0
Excess tax benefits from share-based compensation	961	13,561	62
Net cash provided by financing activities	158,392	338	2,671
Effect of exchange rate changes on cash and cash equivalents	512	(299)	(581)
Net change in cash and cash equivalents	79,321	74,607	(132,659)
Cash and cash equivalents at beginning of period	139,359	64,752	197,411
Cash and cash equivalents at end of period	$ 218,680	$ 139,359	$ 64,752