Activity in the Allowance for Credit Losses (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Components:
Allowance for credit losses		$ 1,776	$ 1,815	$ 1,991	$ 2,094
Provision for loan losses		440	156	338
Provision for Other Credit Losses		4	9	4
Allowance for Loan and Lease Losses, Write-offs		(591)	(470)	(607)
Loan recoveries		108	129	162
Loans and Leases Receivable, Allowance		1,709	1,752	1,937
Unfunded commitments reserve	[1]	$ 67	$ 63	$ 54

[1] The unfunded commitments reserve is recorded in other liabilities in the Consolidated Balance Sheets.