Investments - Unrealized net capital gains and losses included in AOCI (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Fair value
Fixed income securities	$ 58,992,000,000	$ 57,839,000,000
Equity securities	6,621,000,000	5,666,000,000
Short-term investments	1,944,000,000	4,288,000,000
Derivative instruments	2,000,000	5,000,000
Gross unrealized Gains
Fixed income securities	1,750,000,000	1,710,000,000
Equity securities	1,172,000,000	594,000,000
Short-term investments	0	0
Derivative instruments	2,000,000	5,000,000
Gross unrealized Losses
Fixed income securities	(283,000,000)	(447,000,000)
Equity securities	(12,000,000)	(85,000,000)
Short-term investments	0	0
Derivative instruments	(3,000,000)	(3,000,000)
Unrealized net gains (losses)
Fixed income securities	1,467,000,000	1,263,000,000
Equity securities	1,160,000,000	509,000,000
Short-term investments	0	0
Derivative instruments	(1,000,000)	2,000,000
EMA limited partnerships	1,000,000	(4,000,000)
Unrealized net capital gains and losses, pre-tax	2,627,000,000	1,770,000,000
Amounts recognized for:
Insurance reserves	(315,000,000)	0
DAC and DSI	(196,000,000)	(146,000,000)
Amounts recognized	(511,000,000)	(146,000,000)
Deferred income taxes	(454,000,000)	(571,000,000)
Total unrealized net capital gains and losses	1,662,000,000	1,053,000,000
Fair value of derivative securities classified as liabilities, with unrealized net gains (losses) in AOCI	$ 2,000,000
Fair value of derivative securities classified as assets, with unrealized net gains (losses) in AOCI		$ 5,000,000