Investments (Schedule Of Available-For-Sale Securities Whose Value Is Below Amortized Cost) (Details) $ in Millions		12 Months Ended
		Dec. 31, 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		$ 89,488	$ 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		539	1,852
Gross Unrealized Losses		220	907
Gross Unrealized OTTI		$ 12	$ 17
Number of Securities | security	[1]	83	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		$ 174	$ 1,584
Gross Unrealized Losses		52	701
Gross Unrealized OTTI		$ 2	$ 2
Number of Securities | security	[1]	19	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			$ 76
Gross Unrealized Losses			$ 85
Number of Securities | security	[1]		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		$ 1	$ 39
Gross Unrealized Losses		$ 1	$ 38
Number of Securities | security	[1]	2	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		$ 364	$ 153
Gross Unrealized Losses		167	83
Gross Unrealized OTTI		$ 10	$ 15
Number of Securities | security	[1]	62	60

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