Debt Securities (Schedule Of Gross Gains And Gross Losses On Available For Sale Securities) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Gross realized gains	$ 5	$ 16	$ 4
Gross realized losses	(1)	(43)	(1)
Other than Temporary Impairment	0	(1)	(2)
Available-for-sale Securities, Gross Realized Gain (Loss)	$ 4	$ (28)	$ 1

The amount of other than temporary impairment (OTTI) losses on equity securities, OTTI related to credit losses on debt securities, and OTTI losses on debt securities when the entity intends to sell the securities or it is more likely than not that the entity will be required to sell the securities before recovery of its amortized cost basis. Additionally, this item includes OTTI losses recognized during the period on investments accounted for under the cost method of accounting.

No definition available.

Name:	us-gaap_OtherThanTemporaryImpairmentLossesInvestmentsPortionRecognizedInEarningsNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration