Accumulated Other Comprehensive Loss (Reclassification Out of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	$ 314	$ (5,197)	$ (1,032)
Other comprehensive income (loss), tax effect	(71)	1,296	243
Other comprehensive income (loss), net of tax	243	(3,901)	(789)
Available-for-sale securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrealized gains (losses) arising during the period, before tax	338	(5,222)	(859)
Net unrealized gains (losses) arising during the period, tax	(78)	1,240	203
Net unrealized gains (losses) arising during the period, net of tax	260	(3,982)	(656)
Reclassification from AOCI, before tax	5	23	102
Reclassification from AOCI, tax	(1)	(5)	(23)
Reclassification from AOCI, net of tax	4	18	79
Other comprehensive income (loss), before tax	1,244	(5,245)	(961)
Other comprehensive income (loss), tax effect	(295)	1,245	226
Other comprehensive income (loss), net of tax	949	(4,000)	(735)
Available for sale, transferred to held to maturity, parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrealized gains (losses) arising during the period, before tax	911
Net unrealized gains (losses) arising during the period, tax	(218)
Net unrealized gains (losses) arising during the period, net of tax	693
Held-to-maturity securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrealized gains (losses) arising during the period, before tax	(911)
Net unrealized gains (losses) arising during the period, tax	218
Net unrealized gains (losses) arising during the period, net of tax	(693)
Reclassification from AOCI, before tax	(14)
Reclassification from AOCI, tax	3
Reclassification from AOCI, net of tax	(11)
Other comprehensive income (loss), before tax	(897)
Other comprehensive income (loss), tax effect	215
Other comprehensive income (loss), net of tax	(682)
Translation adjustments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	6	(10)
Other comprehensive income (loss), tax effect	(1)	2
Other comprehensive income (loss), net of tax	5	(8)
Net investment hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), before tax	(3)	8
Other comprehensive income (loss), tax effect	1	(1)
Other comprehensive income (loss), net of tax	(2)	7
Cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrealized gains (losses) arising during the period, before tax	(22)	(2)
Net unrealized gains (losses) arising during the period, tax	6	0
Net unrealized gains (losses) arising during the period, net of tax	(16)	(2)
Reclassification from AOCI, before tax	14	21	61
Reclassification from AOCI, tax	(3)	(6)	(14)
Reclassification from AOCI, net of tax	11	15	47
Other comprehensive income (loss), before tax	(36)	(23)
Other comprehensive income (loss), tax effect	9	6
Other comprehensive income (loss), net of tax	(27)	(17)	(47)
Defined benefit pension plans
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net unrealized gains (losses) arising during the period, before tax		2	(11)
Net unrealized gains (losses) arising during the period, tax		0	3
Net unrealized gains (losses) arising during the period, net of tax		2	(8)
Reclassification from AOCI, before tax		(71)	(1)
Reclassification from AOCI, tax		(44)	0
Reclassification from AOCI, net of tax		(115)	(1)
Other comprehensive income (loss), before tax		73	(10)
Other comprehensive income (loss), tax effect		44	3
Other comprehensive income (loss), net of tax	$ 0	$ 117	$ (7)