Fair Values of Assets and Liabilities (Significant Unobservable Level 3 Inputs Nonrecurring Basis) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Commercial Loans Held For Sale | Commercial
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets	$ 5	$ 1
Commercial and Industrial Loans | Commercial
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets	347	366
Commercial Mortgage Loans | Commercial
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets	85	52
Commercial construction loans | Commercial
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets		55
Servicing Rights
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets	685	788
OREO Property
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets	27	36
Bank premises and equipment
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets	$ 12	5
Operating lease equipment
Fair Value Inputs [Line Items]
Fair value measurements nonrecurring assets		$ 39
Minimum | Servicing Rights
Fair Value Inputs [Line Items]
Prepayment speed		0.60%
OAS spread (bps)	364	430
Maximum | Servicing Rights
Fair Value Inputs [Line Items]
Prepayment speed	100.00%	100.00%
OAS spread (bps)	1515	1700
Weighted average | Commercial Loans Held For Sale | Commercial
Fair Value Inputs [Line Items]
Cost to sell	10.00%	10.00%
Weighted average | Fixed | Servicing Rights
Fair Value Inputs [Line Items]
Prepayment speed	14.10%	10.00%
OAS spread (bps)	603	920
Weighted average | Adjustable | Servicing Rights
Fair Value Inputs [Line Items]
Prepayment speed	27.80%	32.20%
OAS spread (bps)	713	640