Securities Available for Sale (Addition Information) (Detail) - USD ($) $ in Millions		Dec. 31, 2018		Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Restricted		$ 3,300		$ 4,300
Available-for-sale Securities	[1],[2]	31,442		30,947	[3]
Federal Home Loan Bank (FHLB) of Atlanta stock (par value)	[4],[5]	227		15
Federal Reserve Bank Stock	[4],[5]	403		403
Mutual Fund Investments	[4],[5]	79		49
Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities		0		72
Fair Value, Measurements, Recurring [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities		31,442	[6]	30,947	[7]
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Debt Securities, Available-for-sale [Line Items]
Available-for-sale Securities		$ 0	[6]	$ 72	[7]

[1] Beginning January 1, 2018, the Company reclassified equity securities previously presented in Securities available for sale to Other assets. Reclassifications have been made to previously reported amounts for comparability.

[2] Includes securities AFS pledged as collateral where counterparties have the right to sell or repledge the collateral of $222 million and $223 million at December?31, 2018 and December?31, 2017, respectively.

[3] Beginning January 1, 2018, the Company reclassified equity securities previously presented in Securities AFS to Other assets on the Consolidated Balance Sheets. Prior periods have been revised to conform to the current presentation for comparability. See Note 11, "Other Assets," for additional information.

[4] Beginning January 1, 2018, the Company reclassified equity securities previously presented in Securities AFS to Other assets on the Consolidated Balance Sheets. Prior periods have been revised to conform to the current presentation for comparability.

[5] Does not include equity securities held for trading purposes classified as Trading assets and derivative instruments or Trading liabilities and derivative instruments on the Company’s Consolidated Balance Sheets. See Note 5, “Trading Assets and Liabilities and Derivative Instruments,” for more information.

[6] Beginning January 1, 2018, the Company reclassified equity securities previously presented in Securities AFS to Other assets on the Consolidated Balance Sheets. Prior periods have been revised to conform to the current presentation for comparability. See Note 11, “Other Assets,” for additional information.

[7] Beginning January 1, 2018, the Company reclassified equity securities previously presented in Securities AFS to Other assets on the Consolidated Balance Sheets. Prior periods have been revised to conform to the current presentation for comparability. See Note 11, “Other Assets,” for additional information.