CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Cash flows from operating activities:
Net income	$ 101,130	$ 90,510	$ 68,616
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	34,307	27,231	33,576
Non-cash, stock-based compensation	14,022	7,944	9,241
Provision for doubtful accounts and sales credits	2,980	1,636	4,865
Amortization of discount on note receivable	(2,325)	(2,488)	0
Impairment of goodwill and intangible assets	0	0	5,500
Gain on sale of business, net of tax	0	(10,040)	0
Realized loss on securities	0	2,783	0
Deferred income taxes	2,713	7,848	4,501
Net tax windfall (shortfall) from stock-based awards	1,136	(1,417)	(452)
Excess tax benefit from stock-based awards	(2,364)	(556)	(175)
Changes in operating assets and liabilities, net of effects of acquisitions:
Accounts receivable	(30,206)	(19,169)	25,253
Prepaid expenses and other assets	(1,455)	1,918	438
Accounts payable and accrued expenses	12,386	8,759	(15,826)
Income taxes receivable/payable	(16,420)	(18,313)	(11,746)
Deferred revenue	(981)	291	(55)
Net cash provided by operating activities	114,923	96,937	123,736
Cash flows from investing activities:
Proceeds from the sales of marketable securities	3,000	21,617	2,133
Proceeds from the maturities of marketable securities	0	150	6,200
Proceeds from disposition of property and equipment	0	2,613	0
Principal payments received on note receivable	3,694	2,652	0
Purchases of property and equipment	(11,154)	(10,029)	(4,625)
Acquisition of business, net of cash acquired	(216,532)	(41,661)	(62,696)
Net cash used in investing activities	(220,992)	(24,658)	(58,988)
Cash flows from financing activities:
Proceeds from borrowings under credit agreement	180,000	0	0
Repayments under credit agreement	(12,500)	0	0
Proceeds from shares issued under employee stock programs	6,945	4,203	2,914
Excess tax benefit from stock-based awards	2,364	556	175
Repurchases and retirement of common stock	(145,035)	(38,556)	(35,148)
Net cash provided by (used in) financing activities	31,774	(33,797)	(32,059)
Effect of foreign currency translations	(3,346)	(2,662)	3,321
Net (decrease) increase in cash and cash equivalents	(77,641)	35,820	36,010
Cash and cash equivalents, beginning of period	194,317	158,497	122,487
Cash and cash equivalents, end of period	116,676	194,317	158,497
Supplemental disclosures of cash flow Information:
Cash paid for interest	995	0	0
Cash paid for income taxes, net	42,784	25,955	33,002
Supplemental disclosure of non-cash investing and financing activities:
Fair value of note receivable issued in connection with disposal of business	0	32,800	0
Common stock issued in connection with acquisition of business	109,359	0	0
Fair value of stock options assumed in connection with acquisition of business	$ 6,944	$ 0	$ 0