Fair Value Option Elected, Difference Between the Aggregate Fair Value and the Aggregate Unpaid Principal Balance (Detail) - USD ($) $ in Millions		Dec. 31, 2018	Dec. 31, 2017
Debt Securities, Trading, and Equity Securities, FV-NI	[1]	$ 5,506	$ 5,093
Loans Held-for-sale, Fair Value Disclosure		1,200	1,600
Loans Receivable, Fair Value Disclosure		163	196
Trading Loans [Member]
Debt Securities, Trading, and Equity Securities, FV-NI		2,540	2,149
Aggregate Unpaid Principal Balance Under the Fair Value Option		(2,526)	(2,111)
Fair Value, Option, Aggregate Differences, Loans and Long-term Receivables		14	38
Loans Held-For-Sale [Member] | Financing Receivables, Equal to Greater than 90 Days Past Due [Member]
Loans Held-for-sale, Fair Value Disclosure			1
Aggregate Unpaid Principal Balance Under the Fair Value Option			(1)
Fair Value, Option, Aggregate Differences, Loans and Long-term Receivables			0
Loans Held-For-Sale [Member] | Performing Financial Instruments [Member]
Loans Held-for-sale, Fair Value Disclosure		1,178	1,576
Aggregate Unpaid Principal Balance Under the Fair Value Option		(1,128)	(1,533)
Fair Value, Option, Aggregate Differences, Loans and Long-term Receivables		50	43
Loans Held-For-Investment [Member] | Performing Financial Instruments [Member]
Loans Receivable, Fair Value Disclosure		158	192
Aggregate Unpaid Principal Balance Under the Fair Value Option		(163)	(198)
Fair Value, Option, Loans Held as Assets, Aggregate Difference		(5)	(6)
Loans Held-For-Investment [Member] | Nonperforming Financing Receivable [Member]
Loans Receivable, Fair Value Disclosure		5	4
Aggregate Unpaid Principal Balance Under the Fair Value Option		(6)	(6)
Fair Value, Option, Loans Held as Assets, Aggregate Amount in Nonaccrual Status, Aggregated Difference		(1)	(2)
Brokered Time Deposits [Member]
Obligations, Fair Value Disclosure		403	236
Aggregate Unpaid Principal Balance Under the Fair Value Option		(403)	(233)
Fair Value, Option, Aggregate Differences, Long-term Debt Instruments		0	3
Long-term Debt [Member]
Obligations, Fair Value Disclosure		289	530
Aggregate Unpaid Principal Balance Under the Fair Value Option		(286)	(517)
Fair Value, Option, Aggregate Differences, Long-term Debt Instruments		$ 3	$ 13

[1] Includes trading securities pledged as collateral where counterparties have the right to sell or repledge the collateral of $1,442 million and $1,086 million at December?31, 2018 and December?31, 2017, respectively.