Reserve for Future Policy Benefits and SA Liabilities Level 4 Changes in Reserve for Future Policy Benefits (Details) - USD ($) $ in Millions	1 Months Ended	5 Months Ended	6 Months Ended
	Jun. 30, 2018	May 31, 2018	Jun. 30, 2017	Jun. 01, 2018	Dec. 31, 2017	Dec. 31, 2016
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross	$ 18,299	$ 14,308	$ 14,191	$ 18,057	$ 14,482	$ 14,000
Liabilities for Guarantees on Long-Duration Contracts, Incurred Benefits	347	402	537
Liabilities for Guarantees on Long-Duration Contracts, Payment for Benefits	(105)	(371)	(444)
Liabilities for Guarantees on Long-Duration Contracts, Other Liability Adjustments	0	(205)	98
Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross	18,299	14,308	14,191	18,057	14,482	14,000
Movement in Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverable [Roll Forward]
Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverable	8,460	5,213	4,884	5,315	5,146	4,756
Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverable, Incurred Benefits, Net	3,157	128	198
Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverables, Payment for Benefits, Net	(12)	(61)	(70)
Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverable	8,460	5,213	4,884	5,315	5,146	4,756
Guaranteed Minimum Death Benefit [Member]
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross	470	884	767	471	873	786
Liabilities for Guarantees on Long-Duration Contracts, Incurred Benefits	8	56	33
Liabilities for Guarantees on Long-Duration Contracts, Payment for Benefits	(9)	(45)	(52)
Liabilities for Guarantees on Long-Duration Contracts, Other Liability Adjustments	0	0	0
Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross	470	884	767	471	873	786
Movement in Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverable [Roll Forward]
Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverable	292	463	411	294	464	432
Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverable, Incurred Benefits, Net	5	36	22
Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverables, Payment for Benefits, Net	(7)	(37)	(43)
Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverable	292	463	411	294	464	432
Secondary Guarantees [Member] | Universal Life [Member]
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross	3,112	3,057	2,776	3,057	2,940	2,627
Liabilities for Guarantees on Long-Duration Contracts, Incurred Benefits	55	117	149
Liabilities for Guarantees on Long-Duration Contracts, Other Liability Adjustments	0	0	0
Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross	3,112	3,057	2,776	3,057	2,940	2,627
Movement in Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverable [Roll Forward]
Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverable	3,112	3,057	2,776	3,057	2,940	2,627
Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverable, Incurred Benefits, Net	55	117	149
Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverable	3,112	3,057	2,776	3,057	2,940	2,627
Annuitization Benefit [Member]
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross	14,717	10,367	10,648	14,529	10,669	10,587
Liabilities for Guarantees on Long-Duration Contracts, Incurred Benefits	284	229	355
Liabilities for Guarantees on Long-Duration Contracts, Payment for Benefits	(96)	(326)	(392)
Liabilities for Guarantees on Long-Duration Contracts, Other Liability Adjustments	0	(205)	98
Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross	14,717	10,367	10,648	14,529	10,669	10,587
Movement in Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverable [Roll Forward]
Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverable	5,056	1,693	1,697	1,964	1,742	1,697
Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverable, Incurred Benefits, Net	3,097	(25)	27
Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverables, Payment for Benefits, Net	(5)	(24)	(27)
Liabilities for Guarantees on Long-Duration Contracts, Reinsurance Recoverable	$ 5,056	$ 1,693	$ 1,697	$ 1,964	$ 1,742	$ 1,697