Deferred Policy Acquisition Costs - Progression of deferred policy acquisition costs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
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	$ 1,156	$ 881	$ 1,239	$ 1,184
Deferred policy acquisition costs and present value of future profits, additions	194	181	619	583
Deferred policy acquisition costs and present value of future profits, periodic amortization	(192)	(185)	(555)	(519)
Deferred policy acquisition costs and present value of future profits, change included in realized gains	4	1	7	6
Deferred policy acquisition costs and present value of future profits, foreign currency translation	1	(1)	2	(2)
Deferred policy acquisition costs and present value of future profits, change in unrealized	(44)	(10)	(193)	(385)
Deferred policy acquisition costs and present value of future profits, ending balance	1,119	867	1,119	867
P&C
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs, beginning balance	258	234	238	226
Deferred policy acquisition costs, additions	149	132	439	403
Deferred policy acquisition costs, periodic amortization	(142)	(134)	(413)	(396)
Deferred policy acquisition costs, foreign currency translation	1	(1)	2	(2)
Deferred policy acquisition costs, ending balance	266	231	266	231
Annuity and Run-off Long-term Care and Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs, beginning balance	1,167	1,089	1,110	1,018
Deferred policy acquisition costs, additions	44	48	177	172
Deferred policy acquisition costs, periodic amortization	(44)	(42)	(122)	(99)
Deferred policy acquisition costs, change included in realized gains	4	1	6	5
Deferred policy acquisition costs, ending balance	1,171	1,096	1,171	1,096
Movement in Deferred Sales Inducements [Roll Forward]
Deferred sales inducements, beginning balance	103	116	110	119
Deferred sales inducements, additions	1	1	3	8
Deferred sales inducements, periodic amortization	(4)	(6)	(14)	(17)
Deferred sales inducements, change included in realized gains	0	0	1	1
Deferred sales inducements, ending balance	100	111	100	111
Movement in Present Value of Future Insurance Profits [Roll Forward]
Present value of future profits, beginning balance	42	51	46	55
Present value of future profits, periodic amortization	(2)	(3)	(6)	(7)
Present value of future profits, ending balance	40	48	40	48
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	(414)	(609)	(265)	(234)
Unrealized investment gains (losses), change in unrealized	(44)	(10)	(193)	(385)
Unrealized investment gains (losses), ending balance	(458)	(619)	(458)	(619)
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	898	647	1,001	958
Deferred policy acquisition costs and present value of future profits, additions	45	49	180	180
Deferred policy acquisition costs and present value of future profits, periodic amortization	(50)	(51)	(142)	(123)
Deferred policy acquisition costs and present value of future profits, change included in realized gains	4	1	7	6
Deferred policy acquisition costs and present value of future profits, change in unrealized	(44)	(10)	(193)	(385)
Deferred policy acquisition costs and present value of future profits, ending balance	853	636	853	636
Excluding Unrealized Gains | Annuity and Run-off Long-term Care and Life
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	1,312	1,256	1,266	1,192
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	$ 1,311	$ 1,255	$ 1,311	$ 1,255