Investments (Schedule Of Available-For-Sale Securities Whose Value Is Below Amortized Cost) (Details) $ in Millions		9 Months Ended	12 Months Ended
		Sep. 30, 2016 USD ($) security	Dec. 31, 2015 USD ($) security
Available For Sale Securities In Unrealized Loss Position With Loss Severity Greater Than 20 Percent [Line Items]
Fair Value		$ 93,505	$ 85,799
Fair Value Decline, Greater Than 20% [Member]
Available For Sale Securities In Unrealized Loss Position With Loss Severity Greater Than 20 Percent [Line Items]
Fair Value		515	1,852
Gross Unrealized Losses		228	907
Gross Unrealized OTTI		$ 15	$ 17
Number of Securities | security	[1]	106	219
Fair Value Decline, Greater Than 20% [Member] | Less than six months
Available For Sale Securities In Unrealized Loss Position With Loss Severity Greater Than 20 Percent [Line Items]
Fair Value		$ 93	$ 1,584
Gross Unrealized Losses		29	701
Gross Unrealized OTTI		$ 2	$ 2
Number of Securities | security	[1]	18	138
Fair Value Decline, Greater Than 20% [Member] | Six months or greater, but less than nine months
Available For Sale Securities In Unrealized Loss Position With Loss Severity Greater Than 20 Percent [Line Items]
Fair Value		$ 4	$ 76
Gross Unrealized Losses		1	$ 85
Gross Unrealized OTTI		$ 1
Number of Securities | security	[1]	4	19
Fair Value Decline, Greater Than 20% [Member] | Nine months or greater, but less than twelve months
Available For Sale Securities In Unrealized Loss Position With Loss Severity Greater Than 20 Percent [Line Items]
Fair Value		$ 92	$ 39
Gross Unrealized Losses		$ 36	$ 38
Number of Securities | security	[1]	13	2
Fair Value Decline, Greater Than 20% [Member] | Twelve months or greater
Available For Sale Securities In Unrealized Loss Position With Loss Severity Greater Than 20 Percent [Line Items]
Fair Value		$ 326	$ 153
Gross Unrealized Losses		162	83
Gross Unrealized OTTI		$ 12	$ 15
Number of Securities | security	[1]	71	60

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