Derivatives and Hedging Activities - Fair Value of Derivative Assets by Type (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Credit Derivatives [Line Items]
Derivative assets before collateral	$ 987	$ 564
Less: Related collateral	207	33
Total derivative assets	780	531
Interest Rate [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	848	308
Foreign Exchange Contract [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	30	60
Commodity [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	95	187
Credit [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	0	0
Other [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	$ 14	$ 9