Deferred Policy Acquisition Costs - Progression of deferred policy acquisition costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
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	$ 1,184	$ 821	$ 975
Deferred policy acquisition costs and present value of future profits, additions	774	754	703
Deferred policy acquisition costs and present value of future profits, periodic amortization	(722)	(710)	(652)
Deferred policy acquisition costs and present value of future profits, annuity unlocking	29	35	(20)
Deferred policy acquisition costs and present value of future profits, change included in realized gains	8	9	3
Deferred policy acquisition costs and present value of future profits, sale of subsidiaries		(19)
Deferred policy acquisition costs and present value of future profits, foreign currency translation	(3)	(3)	(2)
Deferred policy acquisition costs and present value of future profits, change in unrealized	(31)	297	(186)
Deferred policy acquisition costs and present value of future profits, ending balance	1,239	1,184	821
Property and casualty insurance
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs, beginning balance	226	221	211
Deferred policy acquisition costs, additions	535	519	497
Deferred policy acquisition costs, periodic amortization	(520)	(511)	(485)
Deferred policy acquisition costs, foreign currency translation	(3)	(3)	(2)
Deferred policy acquisition costs, ending balance	238	226	221
Annuity and Run-off Long-term Care and Life
Movement Analysis of Deferred Policy Acquisition Costs [Roll Forward]
Deferred policy acquisition costs, beginning balance	1,018	925	875
Deferred policy acquisition costs, additions	230	224	198
Deferred policy acquisition costs, periodic amortization	(169)	(162)	(130)
Deferred policy acquisition costs, annuity unlocking	25	31	(20)
Deferred policy acquisition costs, change included in realized gains	6	8	2
Deferred policy acquisition costs, sale of subsidiaries		(8)
Deferred policy acquisition costs, ending balance	1,110	1,018	925
Movement in Deferred Sales Inducements [Roll Forward]
Deferred sales inducements, beginning balance	119	132	149
Deferred sales inducements, additions	9	11	8
Deferred sales inducements, periodic amortization	(24)	(26)	(26)
Deferred sales inducements, annuity unlocking	4	4	0
Deferred sales inducements, change included in realized gains	2	1	1
Deferred sales inducements, sale of subsidiaries		(3)
Deferred sales inducements, ending balance	110	119	132
Movement in Present Value of Future Insurance Profits [Roll Forward]
Present value of future profits, beginning balance	55	74	85
Present value of future profits, periodic amortization	(9)	(11)	(11)
Present value of future profits, annuity unlocking	0	0	0
Present value of future profits, sale of subsidiaries		(8)
Present value of future profits, ending balance	46	55	74
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	(234)	(531)	(345)
Unrealized investment gains (losses), change in unrealized	(31)	297	(186)
Unrealized investment gains (losses), ending balance	(265)	(234)	(531)
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	958	600	764
Deferred policy acquisition costs and present value of future profits, additions	239	235	206
Deferred policy acquisition costs and present value of future profits, periodic amortization	(202)	(199)	(167)
Deferred policy acquisition costs and present value of future profits, annuity unlocking	29	35	(20)
Deferred policy acquisition costs and present value of future profits, change included in realized gains	8	9	3
Deferred policy acquisition costs and present value of future profits, sale of subsidiaries		(19)
Deferred policy acquisition costs and present value of future profits, change in unrealized	(31)	297	(186)
Deferred policy acquisition costs and present value of future profits, ending balance	1,001	958	600
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	1,192	1,131	1,109
Deferred policy acquisition costs and present value of future profits, change in unrealized	0	0	0
Deferred policy acquisition costs and present value of future profits, ending balance	$ 1,266	$ 1,192	$ 1,131