Activity in the ALLL by segment (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan losses		$ 397		$ 440	$ 156
Allowance for Loan and Lease Losses, Write-offs		(491)		(591)	(470)
Loan recoveries		124		108	129
Allowance for Loan and Lease Losses, Period Increase (Decrease)		(4)	[1]	0	0
Loans and Leases Receivable, Allowance		1,735		1,709	1,752
Commercial Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan losses		108		329
Allowance for Loan and Lease Losses, Write-offs		(167)		(287)
Loan recoveries		40		35
Allowance for Loan and Lease Losses, Period Increase (Decrease)	[1],[2]	(4)
Loans and Leases Receivable, Allowance		1,101		1,124	1,047
Consumer Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan losses		289		111
Allowance for Loan and Lease Losses, Write-offs		(324)		(304)
Loan recoveries		84		73
Allowance for Loan and Lease Losses, Period Increase (Decrease)		0
Loans and Leases Receivable, Allowance		$ 634		$ 585	$ 705

[1] Related to loans disposed in connection with the sale of PAC. For additional information regarding the sale of PAC, see Note 2, "Acquisitions/Dispositions."

[2] Related to loans disposed in connection with the sale of PAC. For additional information regarding the sale of PAC, see Note 2, "Acquisitions/Dispositions."