Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Operating Activities:
Net earnings	$ 76,722	$ 91,207
Adjustments to reconcile net earnings to net cash provided by operating activities:
Provision for losses on accounts receivable	(467)	1,853
Deferred income tax expense (benefit)	5,481	(1,936)
Excess tax benefits from stock plans	(3,426)	(2,246)
Stock compensation expense	10,600	10,472
Depreciation and amortization	9,545	9,174
Gain on sale of assets	(65)	(30)
Other	282	307
Changes in operating assets and liabilities:
Decrease in accounts receivable	12,968	6,683
Decrease (increase) in other current assets	1,924	(1,415)
Increase in accounts payable and accrued expenses	13,559	30,187
Increase in income taxes payable, net	20,274	33,577
Net cash provided by operating activities	147,397	177,833
Investing Activities:
Increase in short-term investments, net	(15,780)	(89)
Purchase of property and equipment	(17,088)	(21,125)
Proceeds from sale of property and equipment	112	43
Other	358	(1,442)
Net cash used in investing activities	(32,398)	(22,613)
Financing Activities:
Proceeds from issuance of common stock	12,920	7,804
Repurchases of common stock	(21,865)	(19,584)
Excess tax benefits from stock plans	3,426	2,246
Net cash used in financing activities	(5,519)	(9,534)
Effect of exchange rate changes on cash and cash equivalents	9,079	8,320
Increase in cash and cash equivalents	118,559	154,006
Cash and cash equivalents at beginning of period	1,294,356	1,084,465
Cash and cash equivalents at end of period	1,412,915	1,238,471
Interest and Taxes Paid:
Interest	187	4
Income taxes	$ 26,512	$ 26,276