Fair Value (Recurring Fair Value Measurements) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Assets [Abstract]
Available-for-sale Securities, Debt Securities	$ 51,785	$ 52,409
Available-for-sale Securities, Equity Securities	300	409
Short-term investments	926	1,737
Mortgage Loans on Real Estate	8,884	7,262
Derivative assets	3,594	3,893
Net embedded derivatives within asset host contracts	192	214
Separate account assets	100,588	101,735
Liabilities [Abstract]
Derivative liabilities	3,883	1,782
Net embedded derivatives within liability host contracts	3,690	1,324
Long-term debt, at estimated fair value, relating to variable interest entities	804	836
Consolidated Securitization Entities
Assets [Abstract]
Mortgage Loans on Real Estate	136	172
Liabilities [Abstract]
Long-term debt, at estimated fair value, relating to variable interest entities	23	48
Recurring
Assets [Abstract]
Available-for-sale Securities, Debt Securities	51,785	52,409
Available-for-sale Securities, Equity Securities	300	409
Short-term investments	926	1,729
Derivative assets	3,594	3,893
Net embedded derivatives within asset host contracts	241	277
Separate account assets	100,588	101,735
Total assets	157,570	160,624
Liabilities [Abstract]
Derivative liabilities	3,883	1,782
Net embedded derivatives within liability host contracts	3,690	1,324
Total liabilities	7,596	3,154
Recurring | Consolidated Securitization Entities
Assets [Abstract]
Mortgage Loans on Real Estate	136	172
Liabilities [Abstract]
Long-term debt, at estimated fair value, relating to variable interest entities	23	48
Recurring | Interest rate
Assets [Abstract]
Derivative assets	2,151	2,455
Liabilities [Abstract]
Derivative liabilities	2,301	668
Recurring | Foreign currency exchange rate
Assets [Abstract]
Derivative assets	339	205
Liabilities [Abstract]
Derivative liabilities	14	4
Recurring | Credit
Assets [Abstract]
Derivative assets	28	13
Liabilities [Abstract]
Derivative liabilities		1
Recurring | Equity market
Assets [Abstract]
Derivative assets	1,076	1,220
Liabilities [Abstract]
Derivative liabilities	1,568	1,109
Recurring | U.S. corporate
Assets [Abstract]
Available-for-sale Securities, Debt Securities	18,506	16,746
Recurring | U.S. government and agency
Assets [Abstract]
Available-for-sale Securities, Debt Securities	11,550	13,806
Recurring | RMBS
Assets [Abstract]
Available-for-sale Securities, Debt Securities	6,815	8,478
Recurring | Foreign corporate
Assets [Abstract]
Available-for-sale Securities, Debt Securities	5,555	4,954
Recurring | State and political subdivision
Assets [Abstract]
Available-for-sale Securities, Debt Securities	2,914	2,705
Recurring | ABS
Assets [Abstract]
Available-for-sale Securities, Debt Securities	2,561	2,674
Recurring | Foreign government
Assets [Abstract]
Available-for-sale Securities, Debt Securities	1,046	745
Recurring | CMBS
Assets [Abstract]
Available-for-sale Securities, Debt Securities	2,838	2,301
Recurring | Level 1
Assets [Abstract]
Available-for-sale Securities, Debt Securities	5,279	7,998
Available-for-sale Securities, Equity Securities	39	44
Short-term investments	459	59
Derivative assets	47	39
Net embedded derivatives within asset host contracts	0	0
Separate account assets	720	624
Total assets	6,544	8,764
Liabilities [Abstract]
Derivative liabilities	0	0
Net embedded derivatives within liability host contracts	0	0
Total liabilities	0	0
Recurring | Level 1 | Consolidated Securitization Entities
Assets [Abstract]
Mortgage Loans on Real Estate	0	0
Liabilities [Abstract]
Long-term debt, at estimated fair value, relating to variable interest entities	0	0
Recurring | Level 1 | Interest rate
Assets [Abstract]
Derivative assets	9	2
Liabilities [Abstract]
Derivative liabilities	0	0
Recurring | Level 1 | Foreign currency exchange rate
Assets [Abstract]
Derivative assets	0	0
Liabilities [Abstract]
Derivative liabilities	0	0
Recurring | Level 1 | Credit
Assets [Abstract]
Derivative assets	0	0
Liabilities [Abstract]
Derivative liabilities		0
Recurring | Level 1 | Equity market
Assets [Abstract]
Derivative assets	38	37
Liabilities [Abstract]
Derivative liabilities	0	0
Recurring | Level 1 | U.S. corporate
Assets [Abstract]
Available-for-sale Securities, Debt Securities	0	0
Recurring | Level 1 | U.S. government and agency
Assets [Abstract]
Available-for-sale Securities, Debt Securities	5,279	7,998
Recurring | Level 1 | RMBS
Assets [Abstract]
Available-for-sale Securities, Debt Securities	0	0
Recurring | Level 1 | Foreign corporate
Assets [Abstract]
Available-for-sale Securities, Debt Securities	0	0
Recurring | Level 1 | State and political subdivision
Assets [Abstract]
Available-for-sale Securities, Debt Securities	0	0
Recurring | Level 1 | ABS
Assets [Abstract]
Available-for-sale Securities, Debt Securities	0	0
Recurring | Level 1 | Foreign government
Assets [Abstract]
Available-for-sale Securities, Debt Securities	0	0
Recurring | Level 1 | CMBS
Assets [Abstract]
Available-for-sale Securities, Debt Securities	0	0
Recurring | Level 2
Assets [Abstract]
Available-for-sale Securities, Debt Securities	42,598	40,392
Available-for-sale Securities, Equity Securities	124	268
Short-term investments	465	1,623
Derivative assets	3,360	3,630
Net embedded derivatives within asset host contracts	0	0
Separate account assets	99,858	100,965
Total assets	146,541	147,050
Liabilities [Abstract]
Derivative liabilities	2,742	1,326
Net embedded derivatives within liability host contracts	0	0
Total liabilities	2,765	1,374
Recurring | Level 2 | Consolidated Securitization Entities
Assets [Abstract]
Mortgage Loans on Real Estate	136	172
Liabilities [Abstract]
Long-term debt, at estimated fair value, relating to variable interest entities	23	48
Recurring | Level 2 | Interest rate
Assets [Abstract]
Derivative assets	2,142	2,445
Liabilities [Abstract]
Derivative liabilities	1,690	668
Recurring | Level 2 | Foreign currency exchange rate
Assets [Abstract]
Derivative assets	339	205
Liabilities [Abstract]
Derivative liabilities	14	4
Recurring | Level 2 | Credit
Assets [Abstract]
Derivative assets	20	12
Liabilities [Abstract]
Derivative liabilities		1
Recurring | Level 2 | Equity market
Assets [Abstract]
Derivative assets	859	968
Liabilities [Abstract]
Derivative liabilities	1,038	653
Recurring | Level 2 | U.S. corporate
Assets [Abstract]
Available-for-sale Securities, Debt Securities	17,107	15,295
Recurring | Level 2 | U.S. government and agency
Assets [Abstract]
Available-for-sale Securities, Debt Securities	6,271	5,808
Recurring | Level 2 | RMBS
Assets [Abstract]
Available-for-sale Securities, Debt Securities	5,524	7,138
Recurring | Level 2 | Foreign corporate
Assets [Abstract]
Available-for-sale Securities, Debt Securities	4,727	4,263
Recurring | Level 2 | State and political subdivision
Assets [Abstract]
Available-for-sale Securities, Debt Securities	2,897	2,692
Recurring | Level 2 | ABS
Assets [Abstract]
Available-for-sale Securities, Debt Securities	2,350	2,357
Recurring | Level 2 | Foreign government
Assets [Abstract]
Available-for-sale Securities, Debt Securities	1,046	719
Recurring | Level 2 | CMBS
Assets [Abstract]
Available-for-sale Securities, Debt Securities	2,676	2,120
Recurring | Level 3
Assets [Abstract]
Available-for-sale Securities, Debt Securities	3,908	4,019
Available-for-sale Securities, Equity Securities	137	97
Short-term investments	2	47
Derivative assets	187	224
Net embedded derivatives within asset host contracts	241	277
Separate account assets	10	146
Total assets	4,485	4,810
Liabilities [Abstract]
Derivative liabilities	1,141	456
Net embedded derivatives within liability host contracts	3,690	1,324
Total liabilities	4,831	1,780
Recurring | Level 3 | Consolidated Securitization Entities
Assets [Abstract]
Mortgage Loans on Real Estate	0	0
Liabilities [Abstract]
Long-term debt, at estimated fair value, relating to variable interest entities	0	0
Recurring | Level 3 | Interest rate
Assets [Abstract]
Derivative assets	0	8
Liabilities [Abstract]
Derivative liabilities	611	0
Recurring | Level 3 | Foreign currency exchange rate
Assets [Abstract]
Derivative assets	0	0
Liabilities [Abstract]
Derivative liabilities	0	0
Recurring | Level 3 | Credit
Assets [Abstract]
Derivative assets	8	1
Liabilities [Abstract]
Derivative liabilities		0
Recurring | Level 3 | Equity market
Assets [Abstract]
Derivative assets	179	215
Liabilities [Abstract]
Derivative liabilities	530	456
Recurring | Level 3 | U.S. corporate
Assets [Abstract]
Available-for-sale Securities, Debt Securities	1,399	1,451
Recurring | Level 3 | U.S. government and agency
Assets [Abstract]
Available-for-sale Securities, Debt Securities	0	0
Recurring | Level 3 | RMBS
Assets [Abstract]
Available-for-sale Securities, Debt Securities	1,291	1,340
Recurring | Level 3 | Foreign corporate
Assets [Abstract]
Available-for-sale Securities, Debt Securities	828	691
Recurring | Level 3 | State and political subdivision
Assets [Abstract]
Available-for-sale Securities, Debt Securities	17	13
Recurring | Level 3 | ABS
Assets [Abstract]
Available-for-sale Securities, Debt Securities	211	317
Recurring | Level 3 | Foreign government
Assets [Abstract]
Available-for-sale Securities, Debt Securities	0	26
Recurring | Level 3 | CMBS
Assets [Abstract]
Available-for-sale Securities, Debt Securities	$ 162	$ 181