Investments - Gross realized gains and losses on available for sale fixed maturity and equity security investment transactions (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Fixed maturities
Gross realized gains and losses on the sale of available for sale fixed maturity and equity security investments
Gross gains	$ 44	$ 24
Gross losses	(8)	0
Equity securities
Gross realized gains and losses on the sale of available for sale fixed maturity and equity security investments
Gross gains	49	59
Gross losses	$ (3)	$ 0