Fair Value Measurements (Reconciliation of Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs) (Level 3) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019		Mar. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance		$ 991		$ 861
Included in earnings		(91)		1
Purchases/originations/acquisitions		286		38
Settlements		(11)		(135)
Transfers Into Level 3	[1]	15		136
Ending Balance		1,190		901
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held	[2]	(89)		(2)
Residential Mortgage
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance		179		137
Included in earnings		0		(2)
Purchases/originations/acquisitions		0		0
Settlements		(4)		(135)
Transfers Into Level 3		15		136
Ending Balance		190		136
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held		0		(2)
Servicing Contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance		938		858
Included in earnings		(84)		28
Purchases/originations/acquisitions		287		40
Settlements		0		0
Transfers Into Level 3		0		0
Ending Balance		1,141		926
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held		(69)		28
Interest Rate Contract
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance		(1)		3
Included in earnings		24		14
Purchases/originations/acquisitions		(1)		(2)
Settlements		(20)		(11)
Transfers Into Level 3		0		0
Ending Balance		2	[3]	4	[4]
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held		11		11
Equity Contract
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning Balance		(125)		(137)
Included in earnings		(31)		(39)
Purchases/originations/acquisitions		0		0
Settlements		13		11
Transfers Into Level 3		0		0
Ending Balance		(143)		(165)
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held		$ (31)		$ (39)

[1] Includes certain residential mortgage loans originated as held for sale that were transferred to held for invest ment.

[2] Includes interest income and expense .

[3] Net interest rate derivatives include derivative assets and liabilities of $ 11 and $ 9 , respectively , as of March 31, 2019 .

[4] Net interest rate derivatives include derivative assets and liabilities of $ 11 and $ 7 , respectively, as of March 31, 2018 .