Business Segments 1 - Group Reporting Basis to US GAAP Adjustments from previous table (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Net Interest Income	$ 2,026	$ 2,303	$ 2,559
Other Revenues	1,701	1,537	1,604
Provision for Credit Losses		171	(199)
Operating Expenses	4,034	3,313	3,633
Profit (Loss) before Income Tax Expense	(929)	356	729
Total Assets	229,677	214,223	203,375
Debt Extinguishment [Member]
Segment Reporting Information [Line Items]
Net Interest Income		0
Other Revenues		123
Provision for Credit Losses		0
Operating Expenses		0
Profit (Loss) before Income Tax Expense		123
Total Assets		0
Deposit Incentives [Member]
Segment Reporting Information [Line Items]
Net Interest Income	14	15	9
Other Revenues	0	0	0
Provision for Credit Losses	0	0	0
Operating Expenses	21	32	20
Profit (Loss) before Income Tax Expense	(7)	(17)	(11)
Total Assets	(28)	(23)	(10)
Derivatives [Member]
Segment Reporting Information [Line Items]
Net Interest Income	0	0	0
Other Revenues	0	0	0
Provision for Credit Losses	0	0	0
Operating Expenses	0	0	0
Profit (Loss) before Income Tax Expense	0	0	0
Total Assets	(33,163)	(38,651)	(30,866)
Expected Credit Losses [Member]
Segment Reporting Information [Line Items]
Net Interest Income	(4)	(3)	(6)
Other Revenues	0	(1)	0
Provision for Credit Losses	200	32	118
Operating Expenses	0	0	0
Profit (Loss) before Income Tax Expense	(204)	(36)	(124)
Total Assets	(357)	(357)	(386)
Goodwill [Member]
Segment Reporting Information [Line Items]
Net Interest Income	0	0	0
Other Revenues	0	0	0
Provision for Credit Losses	0	0	0
Operating Expenses	91	156	0
Profit (Loss) before Income Tax Expense	(91)	(156)	0
Total Assets	100	191	347
Leases [Member]
Segment Reporting Information [Line Items]
Net Interest Income	23	25
Other Revenues	0	0
Provision for Credit Losses	0	0
Operating Expenses	14	8
Profit (Loss) before Income Tax Expense	9	17
Total Assets	33	15
Loan Origination [Member]
Segment Reporting Information [Line Items]
Net Interest Income	(24)	(27)	(29)
Other Revenues	(2)	0	(3)
Provision for Credit Losses	0	0	0
Operating Expenses	(20)	(19)	(14)
Profit (Loss) before Income Tax Expense	(6)	(8)	(18)
Total Assets	18	38	45
Loans Held for Sale [Member]
Segment Reporting Information [Line Items]
Net Interest Income	0	2	9
Other Revenues	(25)	(1)	6
Provision for Credit Losses	(12)	0	(3)
Operating Expenses	0	0	0
Profit (Loss) before Income Tax Expense	(13)	1	18
Total Assets	0	(5)	45
Other Long-lived Assets Impairment [Member]
Segment Reporting Information [Line Items]
Net Interest Income	0
Other Revenues	0
Provision for Credit Losses	0
Operating Expenses	(264)
Profit (Loss) before Income Tax Expense	264
Total Assets	201
Pension and Other Postretirement Benefit Costs [Member]
Segment Reporting Information [Line Items]
Net Interest Income	0	0	0
Other Revenues	0	0	0
Provision for Credit Losses	0	0	0
Operating Expenses	(15)	(12)	8
Profit (Loss) before Income Tax Expense	15	12	(8)
Total Assets	0	0	(44)
Renewable Energy Tax Credit Investments [Member]
Segment Reporting Information [Line Items]
Net Interest Income	0	0	0
Other Revenues	(11)	(7)	(10)
Provision for Credit Losses	0	0	0
Operating Expenses	0	0	0
Profit (Loss) before Income Tax Expense	(11)	(7)	(10)
Total Assets	2	3	3
Securities Transferred to Held-to-maturity [Member]
Segment Reporting Information [Line Items]
Net Interest Income	0	0	0
Other Revenues	0	0	0
Provision for Credit Losses	0	0	0
Operating Expenses	0	0	0
Profit (Loss) before Income Tax Expense	0	0	0
Total Assets	(38)	(65)	(76)
Other [Member]
Segment Reporting Information [Line Items]
Net Interest Income	0	1	1
Other Revenues	(8)	(12)	(2)
Provision for Credit Losses	0	0	0
Operating Expenses	1	4	(11)
Profit (Loss) before Income Tax Expense	(9)	(15)	10
Total Assets	(11)	6	15
Total Adjustments [Member]
Segment Reporting Information [Line Items]
Net Interest Income	9	13	(16)
Other Revenues	(46)	102	(9)
Provision for Credit Losses	188	32	115
Operating Expenses	(172)	169	3
Profit (Loss) before Income Tax Expense	(53)	(86)	(143)
Total Assets	$ (33,243)	$ (38,848)	$ (30,927)