Activity in the Allowance for Credit Losses (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Dec. 31, 2014	Dec. 31, 2013
Components:
Balance at beginning of period	$ 1,991		$ 2,094
Provision for loan losses	55		106
Provision(Benefit) for unfunded commitments	0		4
Allowance for Loan and Lease Losses, Write-offs	(130)		(151)
Loan recoveries	31		41
Balance at end of period	1,947		2,086
Loans and Leases Receivable, Allowance	1,893		2,040		1,937	2,044
Unfunded commitments reserve	54	[1]	46	[1]
Allowance for credit losses	$ 1,947		$ 2,086

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