Income Taxes (Reconciliation Of Income Tax At Effective Income Tax Rate) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Expense (Benefit), Continuing Operations [Abstract]
Income tax expense at federal statutory rate	$ (157,551)	$ (159,343)	$ (153,199)
State taxes, net of federal benefit	(23,167)	(20,573)	(35,852)
Differences between statutory rate and foreign effective tax rate	27,691	25,178	26,271
Effective Income Tax Rate Reconciliation, Tax Expense (Benefit), Share-based Payment Arrangement, Amount	(8,643)	(9,204)	(7,032)
Capital loss carryforwards expiration	0	0	769,706
Valuation Allowance, Deferred Tax Asset, Increase (Decrease), Amount	(987)	(3,555)	(773,737)
Effective tax rate reconciliation, accrual for uncertain tax positions	(204,673)	7,365	2,637
Other	3,368	2,867	7,327
Income tax (expense) benefit	$ (64,644)	$ 146,477	$ 147,027