Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Cash flows from operating activities:
Net income	$ 181,249	$ 194,599
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property and equipment and amortization of other intangible assets	31,620	32,115
Stock-based compensation	22,129	19,365
Excess tax benefit associated with stock-based compensation	(11,366)	(15,309)
Unrealized Gain (Loss) on Derivatives	4,311	(10,515)
contingent interest payment for debenture	(5,225)	0
Other, net	4,842	3,802
Changes in operating assets and liabilities
Accounts receivable	(1,018)	(233)
Prepaid expenses and other assets	7,369	26,414
Accounts payable and accrued liabilities	(4,778)	(869)
Deferred revenues	41,247	34,615
Deferred Income Taxes	37,245	(21,246)
Net cash provided by operating activities	307,625	262,738
Net Cash Provided By Used In Investing Activities Abstract
Proceeds from maturities and sales of marketable securities	1,283,367	2,118,861
Purchases of marketable securities	(1,747,025)	(2,042,657)
Purchases of property and equipment	(21,891)	(18,747)
Other investing activities	(3,736)	74
Net cash used in investing activities	(489,285)	57,531
Cash flows from financing activities:
Proceeds from issuance of common stock from option exercises and employee stock purchase plans	9,014	8,970
Repurchases of common stock	(335,885)	(446,676)
Proceeds from Issuance of Senior Long-term Debt	492,237	0
Excess tax benefit associated with stock-based compensation	11,366	15,309
Net cash used in financing activities	176,732	(422,397)
Effect of exchange rate changes on cash and cash equivalents	606	266
Net decrease in cash and cash equivalents	(4,322)	(101,862)
Cash and cash equivalents at beginning of period	191,608	339,223
Cash and cash equivalents at end of period	187,286	237,361
Supplemental cash flow disclosures:
Cash paid for interest, net of capitalized interest	42,839	37,507
Cash paid for income taxes, net of refunds received	$ 14,342	$ 34,464