Derivative Financial Instruments - Net Gain (Loss) Recognized in Income on Derivative Instruments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Futures | Net loss on mortgage servicing rights
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	$ (2)
Interest rate swaps and swaptions | Net loss on mortgage servicing rights
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	57
Interest rate swaps and swaptions | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	5
Mortgage-backed securities forwards | Net loss on mortgage servicing rights
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	21
Rate lock commitments and forward agency and loan sales | Net gain (loss) on loan sales
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	35
Forward commitments | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	2
Not designated as hedging instrument
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net	$ 118	$ (33)	$ (40)
Not designated as hedging instrument | Futures | Net loss on mortgage servicing rights
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net		(4)	(1)
Not designated as hedging instrument | Interest rate swaps and swaptions | Net loss on mortgage servicing rights
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net		1	(11)
Not designated as hedging instrument | Interest rate swaps and swaptions | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net		3	2
Not designated as hedging instrument | Mortgage-backed securities forwards | Net loss on mortgage servicing rights
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net		(2)	4
Not designated as hedging instrument | Rate lock commitments and forward agency and loan sales | Net gain (loss) on loan sales
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net		(31)	(34)
Not designated as hedging instrument | Forward commitments | Other noninterest income
Derivative Instruments, Gain (Loss) [Line Items]
Derivative instruments not designated as hedging instruments, gain (loss), net		$ 0	$ 0