Allowance for Expected Credit Losses - Amortized Cost Basis (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Financing Receivable, Credit Quality Indicator [Line Items]
2020	$ 9,138
2019	2,403
2018	2,131
2017	1,411
2016	558
2015	29
Prior	70
Revolving Loans	16,639
Total	32,379	$ 26,309
Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total	26,890	21,267
Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total	5,413	5,008
Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total	64	25
Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total	12	9
Commercial and Financial Segment
Financing Receivable, Credit Quality Indicator [Line Items]
Total	30,564	24,543
Commercial and Financial Segment | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total	25,075	19,501
Commercial and Financial Segment | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total	5,413	5,008
Commercial and Financial Segment | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total	64	25
Commercial and Financial Segment | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total	12	9
Commercial and Financial Segment | Geographic Distribution, Domestic
Financing Receivable, Credit Quality Indicator [Line Items]
2020	4,851
2019	1,482
2018	1,010
2017	947
2016	337
2015	0
Prior	0
Revolving Loans	12,518
Total	21,145
Commercial and Financial Segment | Geographic Distribution, Domestic | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
2020	4,511
2019	438
2018	5
2017	120
2016	200
2015	0
Prior	0
Revolving Loans	12,273
Total	17,547
Commercial and Financial Segment | Geographic Distribution, Domestic | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
2020	340
2019	1,024
2018	976
2017	802
2016	137
2015	0
Prior	0
Revolving Loans	245
Total	3,524
Commercial and Financial Segment | Geographic Distribution, Domestic | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	10
2018	29
2017	25
2016	0
2015	0
Prior	0
Revolving Loans	0
Total	64
Commercial and Financial Segment | Geographic Distribution, Domestic | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	10
2018	0
2017	0
2016	0
2015	0
Prior	0
Revolving Loans	0
Total	10
Commercial and Financial Segment | Non-U.S.
Financing Receivable, Credit Quality Indicator [Line Items]
2020	4,238
2019	372
2018	410
2017	184
2016	24
2015	0
Prior	70
Revolving Loans	4,121
Total	9,419
Commercial and Financial Segment | Non-U.S. | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
2020	3,642
2019	0
2018	0
2017	0
2016	0
2015	0
Prior	0
Revolving Loans	3,886
Total	7,528
Commercial and Financial Segment | Non-U.S. | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
2020	596
2019	372
2018	408
2017	184
2016	24
2015	0
Prior	70
Revolving Loans	235
Total	1,889
Commercial and Financial Segment | Non-U.S. | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	2
2017	0
2016	0
2015	0
Prior	0
Revolving Loans	0
Total	2
Commercial real estate
Financing Receivable, Credit Quality Indicator [Line Items]
Total	1,815	1,766
Commercial real estate | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
Total	1,815	1,766
Commercial real estate | Speculative
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	0
Commercial real estate | Special mention
Financing Receivable, Credit Quality Indicator [Line Items]
Total		0
Commercial real estate | Substandard
Financing Receivable, Credit Quality Indicator [Line Items]
Total	0	$ 0
Commercial real estate | Geographic Distribution, Domestic
Financing Receivable, Credit Quality Indicator [Line Items]
2020	49
2019	549
2018	711
2017	280
2016	197
2015	29
Prior	0
Revolving Loans	0
Total	1,815
Commercial real estate | Geographic Distribution, Domestic | Investment grade
Financing Receivable, Credit Quality Indicator [Line Items]
2020	49
2019	549
2018	711
2017	280
2016	197
2015	29
Prior	0
Revolving Loans	0
Total	1,815
Off Balance Sheet Commitment and Guarantees
Financing Receivable, Credit Quality Indicator [Line Items]
2020	376,975
2019	0
2018	0
2017	0
2016	0
2015	0
Prior	0
Revolving Loans	34,244
Total	411,219
Financing Receivables and Off Balance Sheet Commitments
Financing Receivable, Credit Quality Indicator [Line Items]
2020	386,113
2019	2,403
2018	2,131
2017	1,411
2016	558
2015	29
Prior	70
Revolving Loans	50,883
Total	443,598
Unfunded Loan Commitment | Off Balance Sheet Commitment and Guarantees
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
2015	0
Prior	0
Revolving Loans	30,971
Total	30,971
Indemnified Securities Financing | Off Balance Sheet Commitment and Guarantees
Financing Receivable, Credit Quality Indicator [Line Items]
2020	376,975
2019	0
2018	0
2017	0
2016	0
2015	0
Prior	0
Revolving Loans	0
Total	376,975
Standby Letters of Credit | Off Balance Sheet Commitment and Guarantees
Financing Receivable, Credit Quality Indicator [Line Items]
2020	0
2019	0
2018	0
2017	0
2016	0
2015	0
Prior	0
Revolving Loans	3,273
Total	$ 3,273