Commitments and Contingencies - Credit Extension Commitments Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Other Commitments [Line Items]
Legally binding unfunded commitments syndicated	$ 11,900	$ 12,100
Carrying amount credit extension commitments syndicated	776	779
Deferred revenue	19	17
Other liabilities reserve for unfunded lending commitments	757	762
Notional amount of credit extension commitments under fair value option	5,900	7,000
Unfunded loan commitments
Other Commitments [Line Items]
Fair value carrying amount liabilities	$ 135	$ 173