Activity in the Allowance for Credit Losses (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Components:
Allowance for credit losses		$ 1,783	$ 1,831	$ 1,776	$ 1,815
Provision for loan losses		117	103
Provision for Other Credit Losses		2	(2)
Allowance for Loan and Lease Losses, Write-offs		(146)	(112)
Loan recoveries		34	27
Loans and Leases Receivable, Allowance		1,714	1,770	$ 1,709	$ 1,752
Unfunded commitments reserve	[1]	$ 69	$ 61

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