Commitments and Contingencies - Pledged Assets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Pledged securities	$ 11,283	$ 13,237
Federal Reserve Bank Advances [Member]
Commitments and Contingencies Disclosure [Abstract]
Pledged loans	30,238	30,007
Line of Credit Facility, Remaining Borrowing Capacity	21,169	21,599
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Pledged loans	30,238	30,007
Line of Credit Facility, Remaining Borrowing Capacity	21,169	21,599
FHLB Advances
Commitments and Contingencies Disclosure [Abstract]
Pledged loans	80,816	47,840
Line of Credit Facility, Remaining Borrowing Capacity	66,842	33,349
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Pledged loans	80,816	47,840
Line of Credit Facility, Remaining Borrowing Capacity	$ 66,842	$ 33,349