Revisions To Financial Statements (Schedule Of Prior Period Financial Statements - Stockholder's Equity) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Net income (loss)	$ 251,608
Ending balance,	5,386,602
Retained Earnings [Member]
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Beginning balance,	4,062,696
Net income (loss)	251,608
Ending balance,	4,314,306
As Previously Reported [Member]
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Net income (loss)	251,226
As Previously Reported [Member] | Retained Earnings [Member]
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Beginning balance,	4,070,604
Net income (loss)	251,226
Ending balance,	4,321,830
Impact of Revisions [Member]
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Net income (loss)	382
Impact of Revisions [Member] | Retained Earnings [Member]
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Beginning balance,	(7,908)
Net income (loss)	382
Ending balance,	$ (7,524)