Commitments, Contingencies, Guarantees, and Others - Litigation (Details) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Jul. 31, 2012 USD ($)	Jul. 31, 2012 USD ($) trust summon	Dec. 31, 2018 USD ($)
Loss Contingencies [Line Items]
Loss contingency, estimate of possible loss			$ 1,100
Anti-Money Laundering
Loss Contingencies [Line Items]
Litigation settlement paid			$ 100
Pending Litigation | Interchange Litigation
Loss Contingencies [Line Items]
Litigation settlement, attributable to reporting entity and third party	$ 6,200
GreenPoint Subsidiary | Pending Litigation | FHFA Litigation
Loss Contingencies [Line Items]
Number of summons filed | summon		3
Number of residential mortgage backed securities trusts | trust		3
Mortgage loans sold to third party, face amount under litigation	$ 3,400	$ 3,400