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				6 Months Ended
	Jun. 30, 2019		Jun. 30, 2018		Jun. 30, 2019		Jun. 30, 2018		Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Derivative contracts, net [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	$ 24		$ 3		$ 24		$ 3		$ 16	$ 13	$ 1	$ 0
Included in earnings	52	[1]	24	[2]	87	[1]	18	[2]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	0		0		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0		0		0		0
Sales	0		0		0		0
Settlements	(1)		(1)		(2)		(2)
Transfers to other balance sheet line items	(43)	[3]	(23)	[4]	(74)	[3]	(17)	[4]
Transfers into Level 3	0		0		0		0
Transferred Out of Level 3 in The Fair Value Hierarchy	0		0		0		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	30		17		30		16
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value			0				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				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				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				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	127		177		127		177		$ 134	$ 163	$ 188	$ 196
Included in earnings	1	[5]	(1)	[6]	3	[5]	(3)	[6]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	0		0		0		0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0		0		0		0
Sales	0		0		0		0
Settlements	(8)		(10)		(15)		(17)
Transfers to other balance sheet line items	0		0		0		0
Transfers into Level 3	0		0		1		1
Transferred Out of Level 3 in The Fair Value Hierarchy	0		0		(25)		0
Fair Value, Assets Measured on Recurring Basis, Change in Unrealized Gain (Loss)	1		(1)		2		(4)
Interest Rate Lock Commitments [Member]
Transferred Out of Level 3 in The Fair Value Hierarchy	$ (43)		$ 23		$ (74)		$ 17

[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 $30 million in earnings during both the three and six months ended June 30, 2019, related to changes in unrealized gains on net derivative instruments still held at June 30, 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 $17 million and $16 million in earnings during the three and six months ended June 30, 2018, respectively, related to changes in unrealized gains on net derivative instruments still held at June 30, 2018.

[3] During the three and six months ended June 30, 2019, the Company transferred $43 million and $74 million, respectively, of net IRLC assets out of level 3 as the associated loans were closed.

[4] uring the three and six months ended June 30, 2018, the Company transferred $23 million and $17 million, respectively, of net IRLC assets 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 and $2 million in earnings during the three and six months ended June 30, 2019, respectively, related to changes in unrealized gains on LHFI still held at June 30, 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 $1 million and $4 million in earnings during the three and six months ended June 30, 2018, respectively, related to changes in unrealized losses on LHFI still held at June 30, 2018.