Fair Value Option Elected, Difference Between the Aggregate Fair Value and the Aggregate Unpaid Principal Balance (Detail) - USD ($) $ in Millions		Sep. 30, 2019	Dec. 31, 2018
Debt Securities, Trading, and Equity Securities, FV-NI	[1]	$ 7,104	$ 5,506
Loans Receivable, Fair Value Disclosure		124	163
Trading Loans [Member]
Debt Securities, Trading, and Equity Securities, FV-NI		2,862	2,540
Aggregate Unpaid Principal Balance Under the Fair Value Option		(2,779)	(2,526)
Fair Value, Option, Aggregate Differences, Loans and Long-term Receivables		83	14
Trading Liabilities, Fair Value Disclosure		9
Aggregate Unpaid Principal Balance Under the Fair Value Option, Liabilities		9
Fair Value Option, Aggregate Differences, Liabilities		0
Loans Held-For-Sale [Member] | Performing Financial Instruments [Member]
Loans Held-for-sale, Fair Value Disclosure		1,488	1,178
Aggregate Unpaid Principal Balance Under the Fair Value Option		(1,446)	(1,128)
Fair Value, Option, Aggregate Differences, Loans and Long-term Receivables		42	50
Loans Held-For-Investment [Member] | Performing Financial Instruments [Member]
Loans Receivable, Fair Value Disclosure		121	158
Aggregate Unpaid Principal Balance Under the Fair Value Option		(119)	(163)
Fair Value, Option, Loans Held as Assets, Aggregate Difference		2	(5)
Loans Held-For-Investment [Member] | Nonperforming Financing Receivable [Member]
Loans Receivable, Fair Value Disclosure		3	5
Aggregate Unpaid Principal Balance Under the Fair Value Option		(4)	(6)
Fair Value, Option, Loans Held as Assets, Aggregate Amount in Nonaccrual Status, Aggregated Difference		(1)	(1)
Brokered Time Deposits [Member]
Obligations, Fair Value Disclosure		552	403
Aggregate Unpaid Principal Balance Under the Fair Value Option, Liabilities		539	403
Fair Value Option, Aggregate Differences, Liabilities		13	0
Long-term Debt [Member]
Obligations, Fair Value Disclosure		302	289
Aggregate Unpaid Principal Balance Under the Fair Value Option, Liabilities		290	286
Fair Value, Option, Aggregate Differences, Long-term Debt Instruments		$ 12	$ 3

[1] Includes trading securities pledged as collateral where counterparties have the right to sell or repledge the collateral of $1,284 million and $1,442 million at September 30, 2019 and December 31, 2018, respectively.