Commitments, Contingencies and Guarantees - Schedule of Commitments, Contingencies and Guarantees (Details) $ in Millions	Sep. 30, 2017 USD ($)
Commitments to extend credit
Commitment, Contingencies and Guarantees disclosures
Commitments	$ 30,425
Issued standby and commercial letters of credit
Commitment, Contingencies and Guarantees disclosures
Commitments	5,551
Commitments to enter into forward-starting resale agreements
Commitment, Contingencies and Guarantees disclosures
Commitments	1,514
Other commitments
Commitment, Contingencies and Guarantees disclosures
Commitments	$ 1,577