Reconciliation of the Beginning and Ending Balances for Fair Valued Assets and Liabilities Measured on a Recurring Basis Using Significant Unobservable Inputs (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019		Mar. 31, 2018		Dec. 31, 2018	Dec. 31, 2017
Derivative contracts, net [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	$ 16		$ 1		$ 13	$ 0
Included in earnings	35	[1]	(6)	[2]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0		0
Sales	0		0
Settlements	(1)		(1)
Transfers to other balance sheet line items	(31)	[3]	6	[4]
Transfers into Level 3	0		0
Transferred Out of Level 3 in The Fair Value Hierarchy	0		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	22		16
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			0			59
Included in earnings			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases			0
Sales			0
Settlements			(2)
Transfers to other balance sheet line items			0
Transfers into Level 3			0
Transferred Out of Level 3 in The Fair Value Hierarchy			(57)
Asset-backed Securities [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			0			8
Included in earnings			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases			0
Sales			0
Settlements			(1)
Transfers to other balance sheet line items			0
Transfers into Level 3			0
Transferred Out of Level 3 in The Fair Value Hierarchy			(7)
Corporate Debt Securities [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			0			5
Included in earnings			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases			0
Sales			0
Settlements			0
Transfers to other balance sheet line items			0
Transfers into Level 3			0
Transferred Out of Level 3 in The Fair Value Hierarchy			(5)
Available-for-sale Securities [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			0			72
Included in earnings			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)			0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases			0
Sales			0
Settlements			(3)
Transfers to other balance sheet line items			0
Transfers into Level 3			0
Transferred Out of Level 3 in The Fair Value Hierarchy			(69)
Loans Held-For-Investment [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	134		188		$ 163	$ 196
Included in earnings	2	[5]	(2)	[6]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0		0
Sales	0		0
Settlements	(7)		(7)
Transfers to other balance sheet line items	0		0
Transfers into Level 3	1		1
Transferred Out of Level 3 in The Fair Value Hierarchy	(25)		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	1		(3)
Interest Rate Lock Commitments [Member]
Transferred Out of Level 3 in The Fair Value Hierarchy	$ (31)		$ 6

[1] Includes issuances, fair value changes, and expirations. Amount related to residential IRLCs is recognized in Mortgage related income, amount related to commercial IRLCs is recognized in Commercial real estate related income, and amount related to Visa derivative liability is recognized in Other noninterest expense. Included $22 million in earnings during the three months ended March 31, 2019, related to changes in unrealized gains on net derivative instruments still held at March 31, 2019.

[2] Includes issuances, fair value changes, and expirations. Amount related to residential IRLCs is recognized in Mortgage related income, amount related to commercial IRLCs is recognized in Commercial real estate related income, and amount related to Visa derivative liability is recognized in Other noninterest expense. Included $16 million in earnings during the three months ended March 31, 2018, related to changes in unrealized gains on net derivative instruments still held at March 31, 2018.

[3] During the three months ended March 31, 2019, the Company transferred $31 million of net IRLC assets out of level 3 as the associated loans were closed.

[4] uring the three months ended March 31, 2018, the Company transferred $6 million of net IRLC liabilities out of level 3 as the associated loans were closed.

[5] Amounts are generally included in Mortgage related income; however, the mark on certain fair value loans is included in Other noninterest income. Included $1 million in earnings during the three months ended March 31, 2019, related to changes in unrealized gains on LHFI still held at March 31, 2019.

[6] Amounts are generally included in Mortgage related income; however, the mark on certain fair value loans is included in Other noninterest income. Included $3 million in earnings during the three months ended March 31, 2018, related to changes in unrealized losses on LHFI still held at March 31, 2018.