Revisions To Financial Statements (Schedule Of Prior Period Financial Statements - Stockholder's Equity) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2019
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Net income (loss)	$ 280,922		$ 532,530
Ending balance,	5,735,239		5,735,239
Retained Earnings [Member]
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Beginning balance,	4,314,306	$ 4,062,696	4,062,696
Net income (loss)	280,922	251,608
Ending balance,	4,595,227	4,314,306	4,595,227
As Previously Reported [Member]
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Net income (loss)	281,904		533,130
Ending balance,	5,743,746		5,743,746
As Previously Reported [Member] | Retained Earnings [Member]
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Beginning balance,	4,321,830	4,070,604	4,070,604
Net income (loss)	281,904	251,226
Ending balance,	4,603,734	4,321,830	4,603,734
Impact of Revisions [Member]
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Net income (loss)	(982)		(600)
Ending balance,	(8,507)		(8,507)
Impact of Revisions [Member] | Retained Earnings [Member]
Error Corrections And Prior Period Adjustments Restatement [Line Items]
Beginning balance,	(7,524)	(7,908)	(7,908)
Net income (loss)	(982)	382
Ending balance,	$ (8,507)	$ (7,524)	$ (8,507)