Investment Securities (Contractual Maturity of Securities) (Details) - USD ($) $ in Millions		Mar. 31, 2020	Dec. 31, 2019
Debt Securities [Line Items]
Available for Sale Securities, Amortized Cost, 1 year or less		$ 779
Available for Sale Securities, Amortized Cost, After 1 year through 5 years		16,286
Available for Sale Securities, Amortized Cost, After 5 years through 10 years		9,634
Available for Sale Securities, Amortized Cost, After 10 years		59,525
Securities available for sale debt securities, amortized cost		86,224	$ 67,790
Available-for-sale Securities, Fair value, 1 year or less		785
Available-for-sale Securities, Fair value, After 1 year through 5 years		16,788
Available-for-sale Securities, Fair value, After 5 years through 10 years		10,017
Available-for-sale Securities, Fair value, After 10 years		61,487
Available-for-sale Securities, Fair value, Total		$ 89,077	69,163
Weighted-average yield, GAAP basis, available for sale securities		2.89%
Held to Maturity Securities, Amortized Cost, 1 year or less		$ 32
Held to Maturity Securities, Amortized Cost, After 1 year through 5 years		583
Held to Maturity Securities, Amortized Cost, After 5 years through 10 years		434
Held to Maturity Securities, Amortized Cost, After 10 years		420
Held to maturity securities, amortized cost	[1]	1,469	17,661
Held-to-maturity Securities, Fair Value, 1 year or less		32
Held-to-maturity Securities, Fair Value, After 1 year through 5 years		613
Held-to-maturity Securities, Fair Value, After 5 years through 10 years		516
Held-to-maturity Securities, Fair Value, After 10 years		460
Held-to-maturity Securities, Debt Maturities, Fair Value, Total		$ 1,621	$ 18,044
Weighted-average yield, GAAP basis, held to maturity securities		3.26%
One Year or Less [Member]
Debt Securities [Line Items]
Weighted-average yield, GAAP basis, available for sale securities		3.10%
Weighted-average yield, GAAP basis, held to maturity securities		3.32%
After One Year Through Five Years [Member]
Debt Securities [Line Items]
Weighted-average yield, GAAP basis, available for sale securities		2.16%
Weighted-average yield, GAAP basis, held to maturity securities		3.23%
After Five Years Through Ten Years [Member]
Debt Securities [Line Items]
Weighted-average yield, GAAP basis, available for sale securities		2.58%
Weighted-average yield, GAAP basis, held to maturity securities		3.87%
After Ten Years [Member]
Debt Securities [Line Items]
Weighted-average yield, GAAP basis, available for sale securities		3.14%
Weighted-average yield, GAAP basis, held to maturity securities		2.63%
US Treasury and Government [Member]
Debt Securities [Line Items]
Available for Sale Securities, Amortized Cost, 1 year or less		$ 249
Available for Sale Securities, Amortized Cost, After 1 year through 5 years		10,949
Available for Sale Securities, Amortized Cost, After 5 years through 10 years		3,839
Available for Sale Securities, Amortized Cost, After 10 years		1,065
Securities available for sale debt securities, amortized cost		16,102
Held to Maturity Securities, Amortized Cost, After 1 year through 5 years		198
Held to Maturity Securities, Amortized Cost, After 5 years through 10 years		303
Held to Maturity Securities, Amortized Cost, After 10 years		280
Held to maturity securities, amortized cost		781
Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Agency [Member]
Debt Securities [Line Items]
Available for Sale Securities, Amortized Cost, 1 year or less		3
Available for Sale Securities, Amortized Cost, After 1 year through 5 years		117
Available for Sale Securities, Amortized Cost, After 5 years through 10 years		2,092
Available for Sale Securities, Amortized Cost, After 10 years		48,616
Securities available for sale debt securities, amortized cost		50,828
Residential Mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member]
Debt Securities [Line Items]
Available for Sale Securities, Amortized Cost, After 10 years		1,563
Securities available for sale debt securities, amortized cost		1,563
Commercial Mortgage Backed Securities [Member] | Mortgage-backed Securities Agency [Member]
Debt Securities [Line Items]
Available for Sale Securities, Amortized Cost, 1 year or less		7
Available for Sale Securities, Amortized Cost, After 1 year through 5 years		466
Available for Sale Securities, Amortized Cost, After 5 years through 10 years		828
Available for Sale Securities, Amortized Cost, After 10 years		1,880
Securities available for sale debt securities, amortized cost		3,181
Commercial Mortgage Backed Securities [Member] | Mortgage-backed Securities Non-agency [Member]
Debt Securities [Line Items]
Available for Sale Securities, Amortized Cost, After 1 year through 5 years		75
Available for Sale Securities, Amortized Cost, After 5 years through 10 years		351
Available for Sale Securities, Amortized Cost, After 10 years		3,823
Securities available for sale debt securities, amortized cost		4,249
Asset backed [Member]
Debt Securities [Line Items]
Available for Sale Securities, Amortized Cost, 1 year or less		15
Available for Sale Securities, Amortized Cost, After 1 year through 5 years		2,721
Available for Sale Securities, Amortized Cost, After 5 years through 10 years		1,169
Available for Sale Securities, Amortized Cost, After 10 years		1,434
Securities available for sale debt securities, amortized cost		5,339
Held to Maturity Securities, Amortized Cost, After 1 year through 5 years		6
Held to Maturity Securities, Amortized Cost, After 5 years through 10 years		18
Held to Maturity Securities, Amortized Cost, After 10 years		26
Held to maturity securities, amortized cost		50
Other [Member]
Debt Securities [Line Items]
Available for Sale Securities, Amortized Cost, 1 year or less		505
Available for Sale Securities, Amortized Cost, After 1 year through 5 years		1,958
Available for Sale Securities, Amortized Cost, After 5 years through 10 years		1,355
Available for Sale Securities, Amortized Cost, After 10 years		1,144
Securities available for sale debt securities, amortized cost		4,962
Held to Maturity Securities, Amortized Cost, 1 year or less		32
Held to Maturity Securities, Amortized Cost, After 1 year through 5 years		379
Held to Maturity Securities, Amortized Cost, After 5 years through 10 years		113
Held to Maturity Securities, Amortized Cost, After 10 years		114
Held to maturity securities, amortized cost		$ 638

[1] Amounts as of March 31, 2020 are net of the related Allowances for Credit Losses recorded in accordance with the adoption of Accounting Standards Update 2016-13, Financial Instruments - Credit Losses, which totaled $2 million and $19 million for Investment securities and Other assets, respectively. See Recently Adopted Accounting Standards portion of Note 1 Accounting Policies for additional detail on the adoption of this ASU.