Certain Long-Duration Contracts with Guarantees (Liabilities for Guarantee Benefits) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
GMDB | Variable Life, Variable Universal Life and Universal Life Contracts
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Beginning balance	$ 4,143	$ 3,150	$ 2,850
Incurred guarantee benefits	685	927	517
Paid guarantee benefits and other	(15)	(36)	(22)
Change in unrealized investment gains and losses	290	102	(193)
Other	7	0	(2)
Ending balance	5,110	4,143	3,150
GMDB | Annuity Contracts
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Beginning balance	721	714	642
Incurred guarantee benefits	37	98	167
Paid guarantee benefits and other	(74)	(91)	(85)
Change in unrealized investment gains and losses	13	0	(10)
Other	0	0	0
Ending balance	697	721	714
GMIB | Annuity Contracts
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Beginning balance	474	440	467
Incurred guarantee benefits	(20)	(18)	(40)
Paid guarantee benefits and other	(15)	(15)	(16)
Change in unrealized investment gains and losses	(30)	49	41
Other	10	18	(12)
Ending balance	419	474	440
GMAB/GMWB/GMIWB | Annuity Contracts
Movement in Liabilities for Guarantees on Long-Duration Contracts, Guaranteed Benefit Liability, Gross [Roll Forward]
Beginning balance	8,238	8,433	8,182
Incurred guarantee benefits	479	(194)	252
Paid guarantee benefits and other	0	0	0
Change in unrealized investment gains and losses	0	0	0
Other	4	(1)	(1)
Ending balance	$ 8,721	$ 8,238	$ 8,433