Equity (Balance of and Changes in Each Component of AOCI) (Details) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018
Accumulated other comprehensive income		$ 3,801	$ 2,642	$ 3,137	$ 636
Other Comprehensive Income (Loss), before Reclassifications, before Tax		906	2,658
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		2	(95)
Other Comprehensive Income (Loss), Tax		(244)	(557)
Accumulated Translation Adjustment [Member]
Accumulated other comprehensive income		(210)	(123)	(92)	(169)
Other Comprehensive Income (Loss), before Reclassifications, before Tax		(116)	44
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		0	0
Other Comprehensive Income (Loss), Tax		2	(2)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated other comprehensive income	[1]	4,089	2,816	3,299	856
Other Comprehensive Income (Loss), before Reclassifications, before Tax	[1]	1,034	2,617
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax	[1]	0	(98)
Other Comprehensive Income (Loss), Tax	[1]	(244)	(559)
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated other comprehensive income		(78)	(51)	$ (70)	$ (51)
Other Comprehensive Income (Loss), before Reclassifications, before Tax		(12)	(3)
Reclassification from Accumulated Other Comprehensive Income, Current Period, before Tax		2	3
Other Comprehensive Income (Loss), Tax		$ 2	$ 0

[1] Includes cash flow hedges of $(74) and $(26) as of June 30, 2020 and December 31, 2019, respectively, and $(15) and $9 as of June 30, 2019 and December 31, 2018, respectively. See Note 5 – “Derivative Instruments” for additional information on cash flow hedges.