Fair Value Measurements (Fair Values of Assets and Liabilities (Significant Unobservable Level 3 Inputs Nonrecurring Basis)) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Commercial Loans Held For Sale | Commercial
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	$ 5	$ 13
Residential Mortgagel Loans Held For Sale
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets		68
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	412	344
Commercial Mortgage Loans | Commercial
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	15	103
Commercial Construction Loans | Commercial
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	0	6
Commercial Leases | Commercial
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	3
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	744	784
OREO Property
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	42	58
Bank premises and equipment
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	28	83
Operating lease equipment
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	37	42
Private equity investments
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	$ 60	$ 13
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	(11.50%)	(9.20%)
Credit risk factor	0.00%	0.00%
Minimum | Servicing Rights
Quantitative Information About Level 3 Fair Value Measurements
Prepayment speed	0.70%	1.00%
OAS spread (bps)	1.00%	3.64%
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	13.80%	16.50%
Credit risk factor	75.60%	80.50%
Maximum | Servicing Rights
Quantitative Information About Level 3 Fair Value Measurements
Prepayment speed	100.00%	100.00%
OAS spread (bps)	15.15%	15.15%
Maximum | Private equity investments
Quantitative Information About Level 3 Fair Value Measurements
Liquidity discount	37.50%
Weighted-average | Commercial Loans Held For Sale
Quantitative Information About Level 3 Fair Value Measurements
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	2.30%	3.10%
Credit risk factor	1.40%	1.30%
Weighted-average | Private equity investments
Quantitative Information About Level 3 Fair Value Measurements
Liquidity discount	12.80%	18.00%
Weighted-average | Fixed | Servicing Rights
Quantitative Information About Level 3 Fair Value Measurements
Prepayment speed	10.20%	11.80%
OAS spread (bps)	6.54%	6.18%
Weighted-average | Adjustable | Servicing Rights
Quantitative Information About Level 3 Fair Value Measurements
Prepayment speed	25.30%	27.00%
OAS spread (bps)	7.38%	7.03%