Activity in the Allowance for Credit Losses (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Components:
Allowance for credit losses		$ 1,815	$ 1,991	$ 2,094	$ 2,219
Provision for loan losses		156	338	548
Provision for Other Credit Losses		9	4	5
Allowance for Loan and Lease Losses, Write-offs		(470)	(607)	(869)
Loan recoveries		129	162	191
Loans and Leases Receivable, Allowance		1,752	1,937	2,044
Unfunded commitments reserve	[1]	$ 63	$ 54	$ 50

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