Investments (Realized Investment Gains Losses, Net) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Gain (Loss) on Securities [Line Items]
Realized investment gains (losses), net	$ 685	$ (1,092)	$ 1,110	$ (665)
Fixed maturities
Gain (Loss) on Securities [Line Items]
Realized investment gains (losses), net	165	229	243	403
Equity securities
Gain (Loss) on Securities [Line Items]
Realized investment gains (losses), net	0	164	0	420
Commercial mortgage and other loans
Gain (Loss) on Securities [Line Items]
Realized investment gains (losses), net	5	14	17	28
Investment real estate
Gain (Loss) on Securities [Line Items]
Realized investment gains (losses), net	60	6	62	12
LPs/LLCs
Gain (Loss) on Securities [Line Items]
Realized investment gains (losses), net	10	(10)	16	(21)
Derivatives
Gain (Loss) on Securities [Line Items]
Realized investment gains (losses), net	445	(1,496)	773	(1,507)
Other
Gain (Loss) on Securities [Line Items]
Realized investment gains (losses), net	$ 0	$ 1	$ (1)	$ 0