Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income	$ 440,645	$ 375,236	$ 355,260
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation of property and equipment and amortization of other intangible assets	58,167	61,491	63,690
Stock-based compensation	50,044	46,075	43,977
Excess tax benefit associated with stock-based compensation	(25,058)	(18,464)	(6,054)
Unrealized Gain (Loss) on Derivatives	(2,402)	14,130	(2,249)
contingent interest payment for debenture	13,385	10,759	0
Amortization of Financing Costs and Discounts	13,411	12,292	10,878
Other, net	(3,787)	(1,781)	480
Changes in operating assets and liabilities
Accounts receivable	(871)	661	(73)
Prepaid expenses and other assets	8,980	(1,728)	11,571
Accounts payable and accrued liabilities	40,244	21,013	45,419
Deferred revenues	14,347	70,988	34,518
Net deferred income taxes and other long term tax liabilities	87,614	82,328	43,532
Net cash provided by operating activities	667,949	651,482	600,949
Cash flows from investing activities:
Proceeds from maturities and sales of marketable securities	3,817,899	2,767,027	3,428,659
Purchases of marketable securities	(3,691,057)	(3,219,329)	(3,277,096)
Purchases of property and equipment	(26,574)	(40,656)	(39,327)
Payments to Acquire Intangible Assets	(143,000)	0	0
Other investing activities	2,333	(3,941)	452
Net cash provided by (used in) investing activities	(40,399)	(496,899)	112,688
Cash flows from financing activities:
Proceeds from issuance of common stock from option exercises and employee stock purchase plans	13,670	14,690	17,597
Repurchases of common stock	(662,491)	(643,169)	(883,403)
Proceeds received from borrowing	0	492,237	0
Excess tax benefit associated with stock-based compensation	25,058	18,464	6,054
Net cash used in financing activities	(623,763)	(117,778)	(859,752)
Effect of exchange rate changes on cash and cash equivalents	(501)	246	(1,500)
Net increase (decrease) in cash and cash equivalents	3,286	37,051	(147,615)
Cash and cash equivalents at beginning of period	228,659	191,608	339,223
Cash and cash equivalents at end of period	231,945	228,659	191,608
Supplemental cash flow disclosures:
Cash paid for interest, net of capitalized interest	115,544	99,473	75,088
Cash paid for income taxes, net of refunds received	$ 14,303	$ 39,723	$ 35,201