Commitments, Contingencies and Guarantees (Maximum Potential Obligation) (Details) $ in Millions	Mar. 31, 2020 USD ($)
Commitment Period Two Thousand Twenty Three [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 2,607
Commitment Period Two Thousand Thirty Three [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	3,408
Commitment Period Two Thousand Thirty Four [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	5,750
Commitment Period Two Thousand Thirty Five [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	2,300
Commitment Period Two Thousand Thirty Six [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 5,750