Investment Securities - Contractual Maturities and Weighted-Average Yields of Securities (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Securities available for sale
Due in 1 year or less	$ 505
Due after 1 year through 5 years	4,284
Due after 5 years through 10 years	7,747
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	68,887
Securities available for sale	81,423	$ 79,213
Amortized cost of securities available for sale
Due in 1 year or less	503
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after One Through Five Years, Amortized Cost	4,263
Due after 5 years through 10 years	7,574
Due 10 Years	66,260
Amortized Cost	$ 78,600	77,984
Weighted average yield for securities available for sale
Due in 1 Year or Less	1.49%
Due 1 Year through 5 Years	2.10%
Due 5 Years through 10 Years	2.18%
Due 10 Years	2.82%
Total weighted average yield	2.71%
U.S. Treasury securities
Securities available for sale
Due in 1 year or less	$ 0
Due after 1 year through 5 years	1,549
Due after 5 years through 10 years	2,811
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	0
Securities available for sale	4,360	4,124
Amortized cost of securities available for sale
Amortized Cost	4,333	4,122
RMBS, Agency
Securities available for sale
Due in 1 year or less	0
Due after 1 year through 5 years	68
Due after 5 years through 10 years	912
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	63,477
Securities available for sale	64,457	62,839
Amortized cost of securities available for sale
Amortized Cost	62,126	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	1,284
Securities available for sale	1,284	1,499
Amortized cost of securities available for sale
Amortized Cost	1,195	1,235
RMBS
Securities available for sale
Due in 1 year or less	0
Due after 1 year through 5 years	68
Due after 5 years through 10 years	912
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	64,761
Securities available for sale	65,741	64,338
Amortized cost of securities available for sale
Amortized Cost	$ 63,321	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	2,210
Due after 5 years through 10 years	3,742
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	4,126
Securities available for sale	10,084	9,426
Amortized cost of securities available for sale
Amortized Cost	$ 9,707	9,303
Weighted average yield for securities available for sale
Weighted-average expected life	5 years 3 months 18 days
Other securities
Securities available for sale
Due in 1 year or less	$ 499
Due after 1 year through 5 years	457
Due after 5 years through 10 years	282
Debt Securities, Available-for-sale, Maturity, Allocated and Single Maturity Date, Rolling after 10 Years, Fair Value	0
Securities available for sale	1,238	1,325
Amortized cost of securities available for sale
Amortized Cost	$ 1,239	$ 1,321

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

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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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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