Equity (Balance of and Changes in Each Component of AOCI) (Details) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Accumulated other comprehensive income		$ 4,289	$ 3,258	$ 3,137	$ 636
Other Comprehensive Income (Loss), before Reclassifications, before Tax		1,510	3,530
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		(9)	(167)
Other Comprehensive Income (Loss), Tax		(349)	(741)
Accumulated Translation Adjustment [Member]
Accumulated other comprehensive income		(171)	(157)	(92)	(169)
Other Comprehensive Income (Loss), before Reclassifications, before Tax		(82)	16
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		0	0
Other Comprehensive Income (Loss), Tax		(3)	4
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated other comprehensive income	[1]	4,542	3,472	3,299	856
Other Comprehensive Income (Loss), before Reclassifications, before Tax	[1]	1,610	3,526
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[1]	(12)	(171)
Other Comprehensive Income (Loss), Tax	[1]	(355)	(739)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated other comprehensive income		(82)	(57)	$ (70)	$ (51)
Other Comprehensive Income (Loss), before Reclassifications, before Tax		(18)	(12)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		3	4
Other Comprehensive Income (Loss), Tax		$ 3	$ 2

[1] Includes cash flow hedges of $(57) and $(26) as of September 30, 2020 and December 31, 2019, respectively, and $(47) and $9 as of September 30, 2019 and December 31, 2018, respectively. See Note 5 – “Derivative Instruments” for additional information on cash flow hedges.