Fair Values of Assets and Liabilities (Significant Unobservable Level 3 Inputs Nonrecurring Basis) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Commercial Loans Held For Sale | Commercial
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets	$ 13	$ 33
Residential Mortgagel Loans Held For Sale
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets	68	554
Automobile Loans Held For Sale
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets	2
Credit Card Held For Sale
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets	4
Commercial and Industrial Loans | Commercial
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets	344	456
Commercial Mortgage Loans | Commercial
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets	103	110
Commercial Construction Loans | Commercial
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets	6	23
Residential mortgage loans
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets	55
Mortgage Servicing Rights
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets	784	856
OREO Property
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets	58	90
Bank premises and equipment
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets	83	$ 22
Operating lease equipment
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets	42
Private equity investment funds
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets	$ 13
Minimum | Residential Mortgagel Loans Held For Sale
Fair Value Inputs [Line Items]
Interest rate risk factor	(7.50%)
Minimum | Residential mortgage loans
Fair Value Inputs [Line Items]
Interest rate risk factor	(9.20%)	(7.20%)
Minimum | Mortgage Servicing Rights
Fair Value Inputs [Line Items]
Prepayment speed	1.00%
Discount rate		9.60%
OAS spread (bps)	364
Maximum | Residential Mortgagel Loans Held For Sale
Fair Value Inputs [Line Items]
Interest rate risk factor	0.10%
Maximum | Residential mortgage loans
Fair Value Inputs [Line Items]
Interest rate risk factor	16.50%	17.70%
Credit risk factor	80.50%	46.60%
Maximum | Mortgage Servicing Rights
Fair Value Inputs [Line Items]
Prepayment speed	100.00%	100.00%
Discount rate		13.20%
OAS spread (bps)	1515
Weighted average | Commercial Loans Held For Sale
Fair Value Inputs [Line Items]
Cost to sell		10.00%
Discount rate	4.40%
Weighted average | Residential Mortgagel Loans Held For Sale
Fair Value Inputs [Line Items]
Estimated sales proceeds from comparable transactions		15.00%
Interest rate risk factor	(1.60%)
Credit risk factor	0.10%
Weighted average | Automobile Loans Held For Sale
Fair Value Inputs [Line Items]
Discount rate	3.10%
Weighted average | Residential mortgage loans
Fair Value Inputs [Line Items]
Interest rate risk factor	3.10%	5.00%
Credit risk factor	1.30%	1.80%
Weighted average | Private equity investment funds
Fair Value Inputs [Line Items]
Liquidity discount	18.00%
Weighted average | Fixed Rate | Mortgage Servicing Rights
Fair Value Inputs [Line Items]
Prepayment speed	11.80%	12.00%
Discount rate		9.90%
OAS spread (bps)	618
Weighted average | Adjustable | Mortgage Servicing Rights
Fair Value Inputs [Line Items]
Prepayment speed	27.00%	26.20%
Discount rate		11.80%
OAS spread (bps)	703