Deferred Policy Acquisition Costs - Progression of deferred policy acquisition costs (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Movement Analysis of Deferred Policy Acquisition Costs and Present Value of Future Profits [Roll Forward]
Deferred policy acquisition costs and present value of future profits, beginning balance		$ 1,582	$ 1,156	$ 1,216	$ 1,239
Deferred policy acquisition costs and present value of future profits, additions		247	194	718	619
Deferred policy acquisition costs and present value of future profits, periodic amortization		(236)	(192)	(699)	(555)
Deferred policy acquisition costs and present value of future profits, annuity unlocking				29
Deferred policy acquisition costs and present value of future profits, change included in realized gains		3	4	9	7
Deferred policy acquisition costs and present value of future profits, foreign currency translation		0	1	(1)	2
Deferred policy acquisition costs and present value of future profits, change in unrealized		73	(44)	397	(193)
Deferred policy acquisition costs and present value of future profits, ending balance		1,669	1,119	1,669	1,119
P&C
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs, beginning balance		298	258	270	238
Deferred policy acquisition costs, additions		181	149	524	439
Deferred policy acquisition costs, periodic amortization		(171)	(142)	(485)	(413)
Deferred policy acquisition costs, foreign currency translation		0	1	(1)	2
Deferred policy acquisition costs, ending balance		308	266	308	266
Annuity and Other
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs, beginning balance		1,243	1,167	1,217	1,110
Deferred policy acquisition costs, additions		65	44	192	177
Deferred policy acquisition costs, periodic amortization		(58)	(44)	(193)	(122)
Deferred policy acquisition costs, annuity unlocking				28
Deferred policy acquisition costs, change included in realized gains		3	4	9	6
Deferred policy acquisition costs, ending balance		1,253	1,171	1,253	1,171
Movement in Deferred Sales Inducements [Roll Forward]
Deferred sales inducements, beginning balance		94	103	102	110
Deferred sales inducements, additions		1	1	2	3
Deferred sales inducements, periodic amortization		(5)	(4)	(15)	(14)
Deferred sales inducements, annuity unlocking				1
Deferred sales inducements, change included in realized gains		0	0	0	1
Deferred sales inducements, ending balance		90	100	90	100
Movement in Present Value of Future Insurance Profits [Roll Forward]
Present value of future profits, beginning balance		45	42	49	46
Present value of future profits, periodic amortization		(2)	(2)	(6)	(6)
Present value of future profits, annuity unlocking				0
Present value of future profits, ending balance		43	40	43	40
Movement in Unrealized Gains (Losses) Related to Deferred Policy Acquisition Costs and Present Value of Future Profits [Roll Forward]
Unrealized investment gains (losses), beginning balance	[1]	(98)	(414)	(422)	(265)
Unrealized investment gains (losses), change in unrealized	[1]	73	(44)	397	(193)
Unrealized investment gains (losses), ending balance	[1]	(25)	(458)	(25)	(458)
Movement Analysis of Deferred Policy Acquisition Costs and Present Value of Future Profits [Roll Forward]
Deferred policy acquisition costs and present value of future profits, beginning balance		1,284	898	946	1,001
Deferred policy acquisition costs and present value of future profits, additions		66	45	194	180
Deferred policy acquisition costs and present value of future profits, periodic amortization		(65)	(50)	(214)	(142)
Deferred policy acquisition costs and present value of future profits, annuity unlocking				29
Deferred policy acquisition costs and present value of future profits, change included in realized gains		3	4	9	7
Deferred policy acquisition costs and present value of future profits, change in unrealized		73	(44)	397	(193)
Deferred policy acquisition costs and present value of future profits, ending balance		1,361	853	1,361	853
Excluding Unrealized Gains | Annuity and Other
Movement Analysis of Deferred Policy Acquisition Costs and Present Value of Future Profits [Roll Forward]
Deferred policy acquisition costs and present value of future profits, beginning balance		1,382	1,312	1,368	1,266
Deferred policy acquisition costs and present value of future profits, change in unrealized		0	0	0	0
Deferred policy acquisition costs and present value of future profits, ending balance		$ 1,386	$ 1,311	$ 1,386	$ 1,311

[1] Unrealized adjustments to DPAC includes net unrealized gains/losses on securities and net unrealized gains/losses on cash flow hedges.