Commitments, Contingencies and Guarantees (Maximum Potential Obligation) (Details) $ in Millions	Sep. 30, 2020 USD ($)
Commitment Period Two Thousand Thirty Four [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 1,243
Commitment Period Two Thousand Thirty Five [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	2,639
Commitment Period Two Thousand Thirty Six [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	3,408
Commitment Period Two Thousand Thirty Seven [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	2,850
Commitment Period Two Thousand Thirty Eight [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	2,300
Commitment Period Two Thousand Thirty Nine [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 11,350