Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net income	$ 375,236	$ 355,260	$ 544,450
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property and equipment and amortization of other intangible assets	61,491	63,690	60,655
Stock-based compensation	46,075	43,977	36,649
Excess tax benefit associated with stock-based compensation	(18,464)	(6,054)	(19,320)
Unrealized loss (gain) on Derivatives	14,130	(2,249)	17,801
contingent interest payment for debenture	10,759	0	0
Amortization of Financing Costs and Discounts	12,292	10,878	9,748
(Gain) loss on Sale of Investments	(185)	5	(18,861)
Other, net	(1,596)	475	4,434
Changes in operating assets and liabilities
Accounts receivable	661	(73)	(2,500)
Prepaid expenses and other assets	(1,728)	11,571	(2,694)
Accounts payable and accrued liabilities	21,013	45,419	19,065
Deferred revenues	70,988	34,518	43,254
Net deferred income taxes and other long term tax liabilities	82,328	43,532	(113,284)
Net cash provided by operating activities	651,482	600,949	579,397
Cash flows from investing activities:
Proceeds from maturities and sales of marketable securities	2,767,027	3,428,659	3,508,569
Purchases of marketable securities	(3,219,329)	(3,277,096)	(3,450,068)
Purchases of property and equipment	(40,656)	(39,327)	(65,594)
Other investing activities	(3,941)	452	(3,969)
Net cash provided by (used in) investing activities	(496,899)	112,688	(11,062)
Cash flows from financing activities:
Proceeds from issuance of common stock from option exercises and employee stock purchase plans	14,690	17,597	20,667
Repurchases of common stock	(643,169)	(883,403)	(1,035,617)
Proceeds received from borrowing	492,237	0	738,297
Repayments of borrowings	0	0	(100,000)
Excess tax benefit associated with stock-based compensation	18,464	6,054	19,320
Net cash used in financing activities	(117,778)	(859,752)	(357,333)
Effect of exchange rate changes on cash and cash equivalents	246	(1,500)	(2,515)
Net increase (decrease) in cash and cash equivalents	37,051	(147,615)	208,487
Cash and cash equivalents at beginning of period	191,608	339,223	130,736
Cash and cash equivalents at end of period	228,659	191,608	339,223
Supplemental cash flow disclosures:
Cash paid for interest, net of capitalized interest	99,473	75,088	58,928
Cash paid for income taxes, net of refunds received	$ 39,723	$ 35,201	$ 26,133