Condensed Consolidated Statement Of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012
Cash flows from operating activities:
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 86,365	$ 91,377
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	28,424	15,555
Amortization of discount or premium of investments	1,323	1,090
Amortization of financing costs and discounts	456	104
Share-based compensation	7,108	6,816
Excess tax benefits from share-based compensation	(3,171)	(1,016)
Provision for doubtful accounts	2,565	3,520
Deferred income taxes	472	(1,012)
(Gain) loss on sale of available-for-sale investments	103	(244)
Decrease (increase) in:
Accounts receivable	(7,495)	(7,032)
Prepaid expenses and other current assets	945	(951)
Other assets	182	(118)
(Decrease) increase in:
Accounts payable and accrued expenses	4,035	168
Income taxes payable	(3,286)	7,112
Deferred revenue	13,049	1,611
Liability for uncertain tax positions	3,867	6,538
Other	(62)	(1)
Net cash provided by operating activities	134,880	123,517
Cash flows from investing activities:
Maturity of certificates of deposit	42,615	8,000
Purchase of certificates of deposit	(22,071)	(34,674)
Sales of available-for-sale investments	82,889	64,581
Purchase of available-for-sale investments	(139,955)	(140,785)
Purchases of property and equipment	(11,116)	(3,902)
Proceeds from sale of assets	1	156
Acquisition of businesses, net of cash received	(81,566)	(25,108)
Purchases of intangible assets	(2,784)	(3,668)
Net cash used in investing activities	(131,987)	(135,400)
Cash flows from financing activities:
Proceeds from Issuance of Long-term Debt	0	245,000
Debt issuance costs	(47)	(1,342)
Repurchases of common stock and restricted stock	(4,513)	(60,261)
Issuance of common stock under employee stock purchase plan	161	109
Exercise of stock options	13,515	4,865
Dividends paid	(33,267)	(29,940)
Excess tax benefits from share-based compensation	3,171	1,016
Proceeds from (Payments for) Other Financing Activities	(171)	0
Net cash used in financing activities	(21,151)	159,447
Effect of exchange rate changes on cash and cash equivalents	(1,241)	591
Net change in cash and cash equivalents	(19,499)	148,155
Cash and cash equivalents	199,181	287,514
Cash and cash equivalents at end of period	$ 199,181	$ 287,514