Fair Value Measurements (Fair Values of Assets and Liabilities (Significant Unobservable Level 3 Inputs Nonrecurring Basis)) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Commercial Loans Held For Sale | Commercial
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	$ 1	$ 5
Commercial and Industrial Loans | Commercial
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	318	347
Commercial Mortgage Loans | Commercial
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	25	85
Commercial construction loans | Commercial
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets		0
Commercial Leases | Commercial
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	2
Servicing Rights
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets		685
OREO Property
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	19	27
Bank premises and equipment
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	15	$ 12
Operating lease equipment
Quantitative Information About Level 3 Fair Value Measurements
Fair value measurements nonrecurring assets	$ 55
Minimum | Residential mortgage loans
Quantitative Information About Level 3 Fair Value Measurements
Interest rate risk factor	(10.60%)	(6.00%)
Credit risk factor	0.00%	0.00%
Minimum | Servicing Rights
Quantitative Information About Level 3 Fair Value Measurements
Prepayment speed	0.70%	0.00%
OAS spread (bps)	4.30%	3.64%
Maximum | Residential mortgage loans
Quantitative Information About Level 3 Fair Value Measurements
Interest rate risk factor	15.40%	16.50%
Credit risk factor	46.20%	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%
Weighted average | Commercial Loans Held For Sale
Quantitative Information About Level 3 Fair Value Measurements
Cost to sell		10.00%
Weighted average | Residential mortgage loans
Quantitative Information About Level 3 Fair Value Measurements
Interest rate risk factor	2.30%	4.40%
Credit risk factor	1.20%	1.40%
Weighted average | Fixed | Servicing Rights
Quantitative Information About Level 3 Fair Value Measurements
Prepayment speed	11.20%	14.10%
OAS spread (bps)	5.28%	6.03%
Weighted average | Adjustable | Servicing Rights
Quantitative Information About Level 3 Fair Value Measurements
Prepayment speed	25.20%	27.80%
OAS spread (bps)	7.57%	7.13%