Fair Value Measurements (Fair Values of Assets and Liabilities (Significant Unobservable Level 3 Inputs Nonrecurring Basis)) (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Commercial Loans Held For Sale | Commercial
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	$ 85	$ 14
Residential Mortgagel Loans Held For Sale
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets		96
Automobile Loans Held For Sale
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets		2
Credit Card Held For Sale
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets		4
Commercial and Industrial Loans | Commercial
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	321	290
Commercial Mortgage Loans | Commercial
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	58	112
Commercial construction loans | Commercial
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	0	9
Commercial Leases | Commercial
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	0
Residential mortgage loans
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets		55
Servicing Rights
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	619	756
OREO Property
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	46	64
Bank premises and equipment
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	67	79
Operating lease equipment
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	39	$ 53
Private Equity Investments
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	$ 63
Minimum | Residential Mortgagel Loans Held For Sale
Quantitative Information About Level 3 Fair Value Measurements
Interest rate risk factor		(7.50%)
Minimum | Residential mortgage loans
Quantitative Information About Level 3 Fair Value Measurements
Interest rate risk factor	(5.00%)	(8.00%)
Credit risk factor	0.00%	0.00%
Minimum | Servicing Rights
Quantitative Information About Level 3 Fair Value Measurements
Prepayment speed	0.00%	1.00%
OAS spread (bps)	1.00%	3.04%
Minimum | Private Equity Investments
Quantitative Information About Level 3 Fair Value Measurements
Liquidity discount	5.00%
Maximum | Residential Mortgagel Loans Held For Sale
Quantitative Information About Level 3 Fair Value Measurements
Interest rate risk factor		0.10%
Maximum | Residential mortgage loans
Quantitative Information About Level 3 Fair Value Measurements
Interest rate risk factor	15.70%	16.30%
Credit risk factor	80.30%	80.50%
Maximum | Servicing Rights
Quantitative Information About Level 3 Fair Value Measurements
Prepayment speed	100.00%	100.00%
OAS spread (bps)	15.15%	15.25%
Maximum | Private Equity Investments
Quantitative Information About Level 3 Fair Value Measurements
Liquidity discount	37.50%
Weighted average | Commercial Loans Held For Sale | Commercial
Quantitative Information About Level 3 Fair Value Measurements
Cost to sell	10.00%
Discount spread		4.40%
Weighted average | Residential Mortgagel Loans Held For Sale
Quantitative Information About Level 3 Fair Value Measurements
Interest rate risk factor		(1.60%)
Credit risk factor		0.10%
Weighted average | Automobile Loans Held For Sale
Quantitative Information About Level 3 Fair Value Measurements
Discount spread		3.10%
Weighted average | Residential mortgage loans
Quantitative Information About Level 3 Fair Value Measurements
Interest rate risk factor	5.10%	4.00%
Credit risk factor	1.20%	0.90%
Weighted average | Private Equity Investments
Quantitative Information About Level 3 Fair Value Measurements
Liquidity discount	12.60%
Weighted average | Fixed | Servicing Rights
Quantitative Information About Level 3 Fair Value Measurements
Prepayment speed	14.90%	11.70%
OAS spread (bps)	6.15%	7.06%
Weighted average | Adjustable | Servicing Rights
Quantitative Information About Level 3 Fair Value Measurements
Prepayment speed	27.10%	32.70%
OAS spread (bps)	7.24%	6.68%