Commitments and Contingencies - Summary (Details) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Investments in affordable housing projects
Tax Credit, Private Equity and Other Equity Method Investments
Carrying amount	$ 3,776	$ 3,684
Amount of future funding commitments included in carrying amount	1,154	1,271
Lending exposure	540	647
Renewable Energy Investments
Tax Credit, Private Equity and Other Equity Method Investments
Carrying amount	107	81
Amount of future funding commitments not included in carrying amount	211	246
Private equity investments
Tax Credit, Private Equity and Other Equity Method Investments
Carrying amount	1,597	1,556
Amount of future funding commitments not included in carrying amount	$ 378	$ 331