Segment Information (Reconciliation of Net Investment Income From Segments to Consolidated) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net Investment Income [Abstract]
Total net investment income	$ 5,223	$ 5,085	$ 4,990
Annuities Segment [Member]
Net Investment Income [Abstract]
Total net investment income	1,140	1,005	1,038
Retirement Plan Services Segment [Member]
Net Investment Income [Abstract]
Total net investment income	924	899	899
Life Insurance Segment [Member]
Net Investment Income [Abstract]
Total net investment income	2,658	2,697	2,643
Group Protection Segment [Member]
Net Investment Income [Abstract]
Total net investment income	307	260	168
Other Operations [Member]
Net Investment Income [Abstract]
Total net investment income	$ 194	$ 224	$ 242