Deferred Policy Acquisition Costs - Progression of deferred policy acquisition costs (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 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		$ 1,417	$ 1,205	$ 1,216	$ 1,239
Deferred policy acquisition costs and present value of future profits, additions		252	218	471	425
Deferred policy acquisition costs and present value of future profits, periodic amortization		(233)	(178)	(463)	(363)
Deferred policy acquisition costs and present value of future profits, annuity unlocking		29		29
Deferred policy acquisition costs and present value of future profits, change included in realized gains		3	1	6	3
Deferred policy acquisition costs and present value of future profits, foreign currency translation		(2)	0	(1)	1
Deferred policy acquisition costs and present value of future profits, change in unrealized		116	(90)	324	(149)
Deferred policy acquisition costs and present value of future profits, ending balance		1,582	1,156	1,582	1,156
P&C
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs, beginning balance		279	243	270	238
Deferred policy acquisition costs, additions		181	151	343	290
Deferred policy acquisition costs, periodic amortization		(160)	(136)	(314)	(271)
Deferred policy acquisition costs, foreign currency translation		(2)	0	(1)	1
Deferred policy acquisition costs, ending balance		298	258	298	258
Annuity and Other
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs, beginning balance		1,208	1,137	1,217	1,110
Deferred policy acquisition costs, additions		70	66	127	133
Deferred policy acquisition costs, periodic amortization		(66)	(36)	(135)	(78)
Deferred policy acquisition costs, annuity unlocking		28		28
Deferred policy acquisition costs, change included in realized gains		3	0	6	2
Deferred policy acquisition costs, ending balance		1,243	1,167	1,243	1,167
Movement in Deferred Sales Inducements [Roll Forward]
Deferred sales inducements, beginning balance		97	105	102	110
Deferred sales inducements, additions		1	1	1	2
Deferred sales inducements, periodic amortization		(5)	(4)	(10)	(10)
Deferred sales inducements, annuity unlocking		1		1
Deferred sales inducements, change included in realized gains		0	1	0	1
Deferred sales inducements, ending balance		94	103	94	103
Movement in Present Value of Future Insurance Profits [Roll Forward]
Present value of future profits, beginning balance		47	44	49	46
Present value of future profits, periodic amortization		(2)	(2)	(4)	(4)
Present value of future profits, annuity unlocking		0		0
Present value of future profits, ending balance		45	42	45	42
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]	(214)	(324)	(422)	(265)
Unrealized investment gains (losses), change in unrealized	[1]	116	(90)	324	(149)
Unrealized investment gains (losses), ending balance	[1]	(98)	(414)	(98)	(414)
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		1,138	962	946	1,001
Deferred policy acquisition costs and present value of future profits, additions		71	67	128	135
Deferred policy acquisition costs and present value of future profits, periodic amortization		(73)	(42)	(149)	(92)
Deferred policy acquisition costs and present value of future profits, annuity unlocking		29		29
Deferred policy acquisition costs and present value of future profits, change included in realized gains		3	1	6	3
Deferred policy acquisition costs and present value of future profits, change in unrealized		116	(90)	324	(149)
Deferred policy acquisition costs and present value of future profits, ending balance		1,284	898	1,284	898
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		1,352	1,286	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		$ 1,382	$ 1,312	$ 1,382	$ 1,312

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