Investments (Details 3) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net Investment Income:
Investment income, before expense	$ 3,306	$ 3,620	$ 4,149
Investment expense	(150)	(161)	(206)
Net investment income	3,156	3,459	3,943
Fixed income securities
Net Investment Income:
Investment income, before expense	2,218	2,447	2,921
Equity securities
Net Investment Income:
Investment income, before expense	110	117	149
Mortgage loans
Net Investment Income:
Investment income, before expense	228	265	372
Limited partnership interests
Net Investment Income:
Investment income, before expense	549	614	541
Short-term investments
Net Investment Income:
Investment income, before expense	9	7	5
Other
Net Investment Income:
Investment income, before expense	$ 192	$ 170	$ 161