Commitments and Contingencies - Credit Extension Commitments Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Legally binding unfunded commitments syndicated	$ 10,500	$ 10,600
Carrying amount credit extension commitments syndicated	1,400	829
Deferred revenue	18	16
Other liabilities reserve for unfunded lending commitments	1,360	813
Notional amount of credit extension commitments under fair value option	3,800	4,400
Unfunded loan commitments
Other Commitments [Line Items]
Fair value carrying amount, liabilities	$ 207	$ 90