Derivative Financial Instruments - Net Gain (Loss) Recognized in Income on Derivative Instruments (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Derivative [Line Items]
Derivative gain (loss)	$ (42)	$ 32
Futures | Net loss on mortgage servicing rights
Derivative [Line Items]
Derivative gain (loss)	1	0
Interest rate swaps and swaptions | Net loss on mortgage servicing rights
Derivative [Line Items]
Derivative gain (loss)	38	13
Mortgage-backed securities forwards | Net loss on mortgage servicing rights
Derivative [Line Items]
Derivative gain (loss)	19	9
Rate lock commitments and forward agency and loan sales | Net gain (loss) on loan sales
Derivative [Line Items]
Derivative gain (loss)	(100)	8
Forward commitments | Other noninterest income
Derivative [Line Items]
Derivative gain (loss)	0	1
Interest rate swaps | Other noninterest income
Derivative [Line Items]
Derivative gain (loss)	$ 0	$ 1