Derivatives and Hedging Activities - Fair Value of Derivative Assets by Type (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Credit Derivatives [Line Items]
Derivative assets before collateral	$ 594	$ 564
Less: Related collateral	68	33
Total derivative assets	526	531
Interest Rate [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	438	308
Foreign Exchange [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	49	60
Commodity [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	96	187
Credit [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	0	0
Other [Member]
Credit Derivatives [Line Items]
Derivative assets before collateral	$ 11	$ 9