Activity in the Allowance for Credit Losses (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013
Components:
Balance at beginning of period		$ 1,886	$ 2,046	$ 1,991	$ 2,094
Provision for loan losses		23	93	107	275
Provision for Other Credit Losses		(9)	0	(7)	7
Allowance for Loan and Lease Losses, Write-offs		(102)	(164)	(356)	(473)
Loan recoveries		31	36	98	122
Balance at end of period		1,847	2,011	1,847	2,011
Loans and Leases Receivable, Allowance						$ 1,786	$ 1,834	$ 1,937	$ 1,968	$ 2,003	$ 2,044
Unfunded commitments reserve	[1]					61			43
Allowance for credit losses		$ 1,886	$ 2,046	$ 1,991	$ 2,094	$ 1,847	$ 1,886	$ 1,991	$ 2,011	$ 2,046	$ 2,094

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