Investments (Schedule Of Available-For-Sale Securities Whose Value Is Below Amortized Cost) (Details) $ in Millions		Dec. 31, 2018 USD ($) security	Dec. 31, 2017 USD ($) security
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Nine months or greater, but less than twelve months		$ 33,630	$ 5,684
Fair Value - Twelve months or greater		8,386	5,820
Fair Value - Total		42,016	11,504
Losses - Nine months or greater, but less than twelve months		1,521	87
Losses - Twelve months or greater		818	358
Gross Unrealized Losses - Total		$ 2,339	$ 445
Number of Securities - Total | security		3,360	1,095
Fair Value Decline, Greater Than 20% [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value - Less than six months		$ 389	$ 156
Fair Value - Six months or greater, but less than nine months		96	2
Fair Value - Nine months or greater, but less than twelve months		11	12
Fair Value - Twelve months or greater		138	209
Fair Value - Total		634	379
Losses - Less than six months		122	57
Losses - Six months or greater, but less than nine months		49	1
Losses - Nine months or greater, but less than twelve months		8	6
Losses - Twelve months or greater		70	77
Gross Unrealized Losses - Total		249	141
OTTI - Less than six months		1	1
OTTI - Twelve months or greater		8	10
OTTI - Total		$ 9	$ 11
Number of Securities - Less than six months | security	[1]	44	26
Number of Securities - Six months or greater, but less than nine months | security	[1]	11	4
Number of Securities - Nine months or greater, but less than twelve months | security	[1]	2	7
Number of Securities - Twelve months or greater | security	[1]	32	49
Number of Securities - Total | security	[1]	89	86

[1] We may reflect a security in more than one aging category based on various purchase dates.