Derivative Instruments (Maturity Of The Notional Amounts Of Derivative Financial Instruments) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Maturity of the notional amounts of derivative financial instruments
Remaining Life Less Than 1 Year		$ 26,766
Remaining Life - 1 - 5 Years		30,944
Remaining Life - 6 - 10 Years		32,286
Remaining Life - 11 - 30 Years		16,945
Remaining Life Over - 30 Years		3,409
Remaining Life - Total Years		110,350	$ 104,926
Interest rate contracts [Member]
Maturity of the notional amounts of derivative financial instruments
Remaining Life Less Than 1 Year	[1]	7,998
Remaining Life - 1 - 5 Years	[1]	20,953
Remaining Life - 6 - 10 Years	[1]	31,378
Remaining Life - 11 - 30 Years	[1]	15,840
Remaining Life Over - 30 Years	[1]	1,213
Remaining Life - Total Years	[1]	$ 77,382
Derivative maturity date		Apr. 20, 2067
Foreign currency contracts [Member]
Maturity of the notional amounts of derivative financial instruments
Remaining Life Less Than 1 Year	[2]	$ 22
Remaining Life - 1 - 5 Years	[2]	247
Remaining Life - 6 - 10 Years	[2]	423
Remaining Life - 11 - 30 Years	[2]	1,090
Remaining Life Over - 30 Years	[2]	44
Remaining Life - Total Years	[2]	$ 1,826
Derivative maturity date		Sep. 18, 2049
Equity market contracts [Member]
Maturity of the notional amounts of derivative financial instruments
Remaining Life Less Than 1 Year		$ 18,746
Remaining Life - 1 - 5 Years		9,692
Remaining Life - 6 - 10 Years		485
Remaining Life - 11 - 30 Years		15
Remaining Life Over - 30 Years		2,152
Remaining Life - Total Years		31,090
Credit contracts [Member]
Maturity of the notional amounts of derivative financial instruments
Remaining Life Less Than 1 Year
Remaining Life - 1 - 5 Years		52
Remaining Life - 6 - 10 Years
Remaining Life - 11 - 30 Years
Remaining Life Over - 30 Years
Remaining Life - Total Years		$ 52

[1] As of December 31, 2017, the latest maturity date for which we were hedging our exposure to the variability in future cash flows for these instruments was April 2067.

[2] As of December 31, 2017, the latest maturity date for which we were hedging our exposure to the variability in future cash flows for these instruments was September 2049.