Assets and Liabilities Measured at Fair Value on a Recurring Basis (Additional Information) (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended		12 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Derivative Assets	[1]	$ 1,449		$ 1,449		$ 1,307
Derivative Liabilities	[2]	565		565		462
Interest Rate Lock Commitments [Member]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3		41	$ 64	138	$ 181
Federal Reserve Bank Stock [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Investments, Fair Value Disclosure		402		402		402
Other Assets [Member] | Fair Value, Measurements, Nonrecurring [Member]
Asset Impairment Charges		$ 1		$ 7		64
Other Assets [Member] | Property Subject to Operating Lease [Member] | Fair Value, Measurements, Nonrecurring [Member]
Asset Impairment Charges						$ 59

[1] At September 30, 2015, $1.4 billion, net of $541 million offsetting cash collateral, is recognized in trading assets and derivative instruments within the Company's Consolidated Balance Sheets. At December 31, 2014, $1.3 billion, net of $449 million offsetting cash collateral, is recognized in trading assets and derivative instruments within the Company's Consolidated Balance Sheets.

[2] At September 30, 2015, $565 million, net of $1.1 billion offsetting cash collateral, is recognized in trading liabilities and derivative instruments within the Company's Consolidated Balance Sheets. At December 31, 2014, $462 million, net of $1.0 billion offsetting cash collateral, is recognized in trading liabilities and derivative instruments within the Company's Consolidated Balance Sheets.