Schedule III - Supplementary Insurance Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplementary Insurance Information, by Segment [Line Items]
DAC and VOBA	$ 3,374	$ 3,997
Future Policy Benefits and Contract Owner Account Balances	65,805	64,848
Unearned Premiums	(1)	(1)
Net Investment Income	3,294	3,354	$ 3,343
Premiums and Fee Income	4,748	5,266	5,024
Interest Credited and Other Benefits to Contract Owners	4,636	5,314	4,698
Amortization of DAC and VOBA	529	415	377
Other Operating Expenses	2,654	2,655	2,684
Premiums Written (Excluding Life)	1,155	974	880
Retirement
Supplementary Insurance Information, by Segment [Line Items]
DAC and VOBA	882	1,165
Future Policy Benefits and Contract Owner Account Balances	33,884	34,024
Unearned Premiums	0	0
Net Investment Income	1,918	1,907	1,819
Premiums and Fee Income	750	1,512	1,350
Interest Credited and Other Benefits to Contract Owners	1,043	1,797	1,425
Amortization of DAC and VOBA	238	198	183
Other Operating Expenses	1,140	1,122	1,156
Premiums Written (Excluding Life)	0	0	0
Investment Management
Supplementary Insurance Information, by Segment [Line Items]
DAC and VOBA	1	2
Future Policy Benefits and Contract Owner Account Balances	0	0
Unearned Premiums	0	0
Net Investment Income	(33)	(5)	(26)
Premiums and Fee Income	675	627	601
Interest Credited and Other Benefits to Contract Owners	0	0	0
Amortization of DAC and VOBA	3	3	4
Other Operating Expenses	558	529	517
Premiums Written (Excluding Life)	0	0	0
Individual Life
Supplementary Insurance Information, by Segment [Line Items]
DAC and VOBA	2,366	2,702
Future Policy Benefits and Contract Owner Account Balances	19,801	19,373
Unearned Premiums	0	0
Net Investment Income	866	875	908
Premiums and Fee Income	1,695	1,663	1,722
Interest Credited and Other Benefits to Contract Owners	1,963	2,001	1,940
Amortization of DAC and VOBA	266	181	157
Other Operating Expenses	272	324	470
Premiums Written (Excluding Life)	0	0	0
Employee Benefits
Supplementary Insurance Information, by Segment [Line Items]
DAC and VOBA	84	75
Future Policy Benefits and Contract Owner Account Balances	2,146	2,099
Unearned Premiums	(1)	(1)
Net Investment Income	108	110	109
Premiums and Fee Income	1,663	1,509	1,405
Interest Credited and Other Benefits to Contract Owners	1,293	1,169	1,051
Amortization of DAC and VOBA	11	16	21
Other Operating Expenses	336	306	289
Premiums Written (Excluding Life)	1,155	974	880
Corporate
Supplementary Insurance Information, by Segment [Line Items]
DAC and VOBA	41	53
Future Policy Benefits and Contract Owner Account Balances	9,974	9,352
Unearned Premiums	0	0
Net Investment Income	435	467	533
Premiums and Fee Income	(35)	(45)	(54)
Interest Credited and Other Benefits to Contract Owners	337	347	282
Amortization of DAC and VOBA	11	17	12
Other Operating Expenses	348	374	252
Premiums Written (Excluding Life)	$ 0	$ 0	$ 0