Condensed Consolidated Statement Of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Cash flows from operating activities:
Net earnings	$ 91,377	$ 84,947
Adjustments to reconcile net earnings to net cash provided by operating activities:
Depreciation and amortization	15,555	14,892
Amortization of discount or premium of investments	1,090	600
Amortization of financing costs and discounts	104	0
Share-based compensation	6,816	6,672
Excess tax benefits from share-based compensation	(1,016)	(13,246)
Provision for doubtful accounts	3,520	4,963
Deferred income taxes	(1,012)	5,394
(Gain) loss on available-for-sale investments	(244)	0
Decrease (increase) in:
Accounts receivable	(7,032)	(7,074)
Prepaid expenses and other current assets	(951)	3,811
Other assets	(118)	153
(Decrease) increase in:
Accounts payable and accrued expenses	168	(1,112)
Income taxes payable	7,112	8,885
Deferred revenue	1,611	9,723
Liability for uncertain tax positions	6,538	(9,668)
Other	(1)	293
Net cash provided by operating activities	123,517	109,233
Cash flows from investing activities:
Maturity of certificates of deposit	8,000	0
Purchase of certificates of deposit	(34,674)	(8,000)
Sales of available-for-sale investments	64,581	20,127
Purchase of available-for-sale investments	(140,785)	(50,192)
Purchases of property and equipment	(3,902)	(5,075)
Proceeds from sale of assets	156	4
Acquisition of businesses, net of cash received	(25,108)	(3,244)
Purchases of intangible assets	(3,668)	(2,616)
Net cash used in investing activities	(135,400)	(48,996)
Cash flows from financing activities:
Issuance of long-term debt	245,000	0
Debt issuance costs	(1,342)	0
Repurchases of common stock and restricted stock	(60,261)	(1,273)
Issuance of common stock under employee stock purchase plan	109	110
Exercise of stock options	4,865	7,001
Dividends paid	(29,940)	(9,463)
Excess tax benefits from share-based compensation	1,016	13,246
Net cash provided by financing activities	159,447	9,621
Effect of exchange rate changes on cash and cash equivalents	591	(420)
Net change in cash and cash equivalents	148,155	69,438
Cash and cash equivalents at beginning of period	139,359	64,752
Cash and cash equivalents at end of period	$ 287,514	$ 134,190