Investments (Details 3) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net Investment Income:
Investment income, before expense	$ 898	$ 790	$ 2,642	$ 2,368
Investment expense	(55)	(42)	(154)	(127)
Net investment income	843	748	2,488	2,241
Fixed income securities
Net Investment Income:
Investment income, before expense	519	508	1,564	1,546
Equity securities
Net Investment Income:
Investment income, before expense	37	31	130	103
Mortgage loans
Net Investment Income:
Investment income, before expense	52	56	157	162
Limited partnership interests
Net Investment Income:
Investment income, before expense	223	136	596	383
Short-term investments
Net Investment Income:
Investment income, before expense	9	4	21	11
Other
Net Investment Income:
Investment income, before expense	$ 58	$ 55	$ 174	$ 163