Insurance (Liabilities for Guarantees) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement In Guaranteed Benefit Liability Gross Rollforward
Balance at January 1,	$ 4,372	$ 3,920	$ 3,769
Incurred guaranteed benefits	461	496	191
Paid guaranteed benefits	(50)	(44)	(40)
Balance at December 31,	4,783	4,372	3,920
Variable Annuity Guarantees: | Guaranteed Minimum Death Benefit
Movement In Guaranteed Benefit Liability Gross Rollforward
Balance at January 1,	451	364	307
Incurred guaranteed benefits	91	102	68
Paid guaranteed benefits	(14)	(15)	(11)
Balance at December 31,	528	451	364
Variable Annuity Guarantees: | Guaranteed Minimum Income Benefit
Movement In Guaranteed Benefit Liability Gross Rollforward
Balance at January 1,	601	524	463
Incurred guaranteed benefits	121	78	62
Paid guaranteed benefits	(2)	(1)	(1)
Balance at December 31,	720	601	524
Universal and Variable Life Contracts | Secondary Guarantees
Movement In Guaranteed Benefit Liability Gross Rollforward
Balance at January 1,	2,989	2,726	2,711
Incurred guaranteed benefits	233	291	43
Paid guaranteed benefits	(34)	(28)	(28)
Balance at December 31,	3,188	2,989	2,726
Universal and Variable Life Contracts | Secondary Guarantees | Foreign Currency Translation
Movement In Guaranteed Benefit Liability Gross Rollforward
Incurred guaranteed benefits	78	119	(80)
Universal and Variable Life Contracts | Paid-Up Guarantees
Movement In Guaranteed Benefit Liability Gross Rollforward
Balance at January 1,	331	306	288
Incurred guaranteed benefits	16	25	18
Paid guaranteed benefits	0	0	0
Balance at December 31,	347	331	306
Ceded
Movement In Guaranteed Benefit Liability Gross Rollforward
Balance at January 1,	451	457	417
Incurred guaranteed benefits	66	(11)	43
Paid guaranteed benefits	6	5	(3)
Balance at December 31,	523	451	457
Ceded | Secondary Guarantees
Movement In Guaranteed Benefit Liability Gross Rollforward
Balance at January 1,	191	218	187
Incurred guaranteed benefits	50	(27)	31
Paid guaranteed benefits	0	0	0
Balance at December 31,	241	191	218
Ceded | Paid-Up Guarantees
Movement In Guaranteed Benefit Liability Gross Rollforward
Balance at January 1,	231	214	201
Incurred guaranteed benefits	11	17	13
Paid guaranteed benefits	0	0	0
Balance at December 31,	242	231	214
Ceded | Guaranteed Minimum Death Benefit
Movement In Guaranteed Benefit Liability Gross Rollforward
Balance at January 1,	24	19	23
Incurred guaranteed benefits	4	0	(1)
Paid guaranteed benefits	6	5	(3)
Balance at December 31,	34	24	19
Ceded | Guaranteed Minimum Income Benefit
Movement In Guaranteed Benefit Liability Gross Rollforward
Balance at January 1,	5	6	6
Incurred guaranteed benefits	1	(1)	0
Paid guaranteed benefits	0	0	0
Balance at December 31,	6	5	6
Net
Movement In Guaranteed Benefit Liability Gross Rollforward
Balance at January 1,	3,921	3,463	3,352
Incurred guaranteed benefits	395	507	148
Paid guaranteed benefits	(56)	(49)	(37)
Balance at December 31,	4,260	3,921	3,463
Net | Secondary Guarantees
Movement In Guaranteed Benefit Liability Gross Rollforward
Balance at January 1,	2,798	2,508	2,524
Incurred guaranteed benefits	183	318	12
Paid guaranteed benefits	(34)	(28)	(28)
Balance at December 31,	2,947	2,798	2,508
Net | Paid-Up Guarantees
Movement In Guaranteed Benefit Liability Gross Rollforward
Balance at January 1,	100	92	87
Incurred guaranteed benefits	5	8	5
Paid guaranteed benefits	0	0	0
Balance at December 31,	105	100	92
Net | Guaranteed Minimum Death Benefit
Movement In Guaranteed Benefit Liability Gross Rollforward
Balance at January 1,	427	345	284
Incurred guaranteed benefits	87	102	69
Paid guaranteed benefits	(20)	(20)	(8)
Balance at December 31,	494	427	345
Net | Guaranteed Minimum Income Benefit
Movement In Guaranteed Benefit Liability Gross Rollforward
Balance at January 1,	596	518	457
Incurred guaranteed benefits	120	79	62
Paid guaranteed benefits	(2)	(1)	(1)
Balance at December 31,	$ 714	$ 596	$ 518