Income Taxes (Summary Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Income Tax Expense (Benefit), Continuing Operations [Abstract]
Net operating loss carryforwards	$ 46,879	$ 56,108
Deductible goodwill and intangible assets	10,473	21,044
Tax credit carryforwards	59,337	86,951
Deferred revenue, accruals and reserves	114,548	106,572
Capital loss carryforwards and book impairment of investments	1,161,772	1,162,320
Other	4,791	5,039
Total deferred tax assets	1,397,800	1,438,034
Valuation allowance	(1,162,101)	(1,162,604)
Net deferred tax assets	235,699	275,430
Property and equipment	(4,212)	(10,787)
Convertible debentures	(590,921)	(538,098)
Other	(2,614)	(3,378)
Deferred Tax Liabilities, Gross	597,747	552,263
Total deferred tax liabilities	$ 362,048	$ 276,833