Investment Securities - Contractual Maturities and Weighted-Average Yields of Securities (Detail) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2020	Dec. 31, 2019
Securities available for sale
Due in 1 year or less	$ 271
Due after 1 year through 5 years	7,528
Due after 5 years through 10 years	5,509
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	74,551
Securities available for sale	87,859	$ 79,213
Amortized cost of securities available for sale
Due in 1 year or less	270
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost	7,486
Due after 5 years through 10 years	5,271
Due 10 Years	71,715
Amortized Cost	$ 84,742	77,984
Weighted average yield for securities available for sale
Due in 1 Year or Less	1.15%
Due 1 Year through 5 Years	1.52%
Due 5 Years through 10 Years	2.38%
Due 10 Years	2.61%
Total weighted average yield	2.49%
U.S. Treasury securities
Securities available for sale
Due in 1 year or less	$ 0
Due after 1 year through 5 years	4,362
Due after 5 years through 10 years	0
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	0
Securities available for sale	4,362	4,124
Amortized cost of securities available for sale
Amortized Cost	4,353	4,122
RMBS, Agency
Securities available for sale
Due in 1 year or less	0
Due after 1 year through 5 years	82
Due after 5 years through 10 years	963
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	69,642
Securities available for sale	70,687	62,839
Amortized cost of securities available for sale
Amortized Cost	68,223	62,003
RMBS, Non-agency
Securities available for sale
Due in 1 year or less	0
Due after 1 year through 5 years	0
Due after 5 years through 10 years	0
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	1,327
Securities available for sale	1,327	1,499
Amortized cost of securities available for sale
Amortized Cost	1,144	1,235
RMBS
Securities available for sale
Due in 1 year or less	0
Due after 1 year through 5 years	82
Due after 5 years through 10 years	963
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	70,969
Securities available for sale	72,014	64,338
Amortized cost of securities available for sale
Amortized Cost	$ 69,367	63,238
Weighted average yield for securities available for sale
Weighted-average expected life	3 years 7 months 6 days
CMBS, Agency
Securities available for sale
Due in 1 year or less	$ 6
Due after 1 year through 5 years	2,550
Due after 5 years through 10 years	4,262
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	3,582
Securities available for sale	10,400	9,426
Amortized cost of securities available for sale
Amortized Cost	$ 9,940	9,303
Weighted average yield for securities available for sale
Weighted-average expected life	5 years
Other securities
Securities available for sale
Due in 1 year or less	$ 265
Due after 1 year through 5 years	534
Due after 5 years through 10 years	284
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	0
Securities available for sale	1,083	1,325
Amortized cost of securities available for sale
Amortized Cost	$ 1,082	$ 1,321

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Available-for-sale Securities, Expected Debt Maturities, Fair Value, Rolling Maturity [Abstract]

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Weighted average yield of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), maturing in second through fifth rolling fiscal year following latest fiscal year. For interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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