Carrying Amounts and Fair Values of the Company's Financial Instruments (Detail) - USD ($) $ in Millions		3 Months Ended	9 Months Ended
		Sep. 30, 2015	Sep. 30, 2015	Dec. 31, 2014
Financial assets
Trading assets	[1]	$ 6,537	$ 6,537	$ 6,202
Available-for-sale Securities	[2]	27,270	27,270	26,770
Loans Held-for-sale, Fair Value Disclosure		1,883	1,883	1,892
Financial liabilities
Long-term Debt, Fair Value		986	986	1,283
Trading liabilities		1,330	1,330	1,227
Reported Value Measurement [Member]
Financial assets
Cash and Cash Equivalents, Fair Value Disclosure		4,916	4,916	8,229
Trading assets		6,537	6,537	6,202
Available-for-sale Securities		27,270	27,270	26,770
Loans Held-for-sale, Fair Value Disclosure		2,032	2,032	3,232
Loans Net Fair Value Disclosure		131,774	131,774	131,175
Financial liabilities
Consumer And Commercial Deposits, Fair Value Disclosure		146,371	146,371	140,567
Long-term Debt, Fair Value		8,444	8,444	13,022
Trading liabilities		1,330	1,330	1,227
Affordable Housing [Member]
Gains (Losses) on Sales of Investment Real Estate		0	(19)
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Financial assets
Trading assets		982	982	1,000
Available-for-sale Securities		3,176	3,176	2,059
Financial liabilities
Long-term Debt, Fair Value		0	0	0
Trading liabilities		939	939	929
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Financial assets
Trading assets		9,326	9,326	9,709
Available-for-sale Securities		23,527	23,527	23,765
Financial liabilities
Long-term Debt, Fair Value		986	986	1,283
Trading liabilities		4,750	4,750	5,408
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Financial assets
Trading assets		38	38	25
Available-for-sale Securities		567	567	946
Financial liabilities
Long-term Debt, Fair Value		0	0	0
Trading liabilities		6	6	5
Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Inputs, Level 1 [Member]
Financial assets
Trading assets		0	0	0
Available-for-sale Securities		0	0	0
Financial liabilities
Trading liabilities		0	0	0
Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Inputs, Level 2 [Member]
Financial assets
Trading assets		565	565	545
Available-for-sale Securities		22,905	22,905	23,048
Financial liabilities
Trading liabilities		4	4	1
Fair Value, Measurements, Recurring [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Inputs, Level 3 [Member]
Financial assets
Trading assets		0	0	0
Available-for-sale Securities		0	0	0
Financial liabilities
Trading liabilities		$ 0	$ 0	$ 0

[1] Includes trading securities pledged as collateral where counterparties have the right to sell or repledge the collateral of $1,152 million and $1,316 million at September 30, 2015 and December 31, 2014, respectively

[2] Includes securities AFS pledged as collateral where counterparties have the right to sell or repledge the collateral of $0 million and $369 million at September 30, 2015 and December 31, 2014, respectively.