Allowance for Credit Losses - Summary of Changes in Allowance for Credit Losses and Related Loan Balance by Product - Additional Information (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016		Dec. 31, 2015	Mar. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans		$ 81,732		$ 82,917	$ 81,458
TDR Loans Carried At Lower Of Amortized Cost Or Fair Value Less Cost To Sell		771		881	778
Affiliated Entity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans		5,107		4,815	5,016
Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans		20,120		20,464
Residential Mortgage [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Additional Charge-off for Loans Transferred to Held-for-Sale	[1]	2
Loans		$ 17,521	[2],[3]	$ 17,758	$ 16,991

[1] For collateral dependent loans that are transferred to held for sale, the existing allowance for credit losses at the time of transfer are recognized as a charge-off. We transferred to held for sale certain residential mortgage loans during the three months ended March 31, 2016 and, accordingly, we recognized the existing allowance for credit losses on these loans as additional charge-off totaling $2 million during the three months ended March 31, 2016.

[2] The decrease in nonaccrual loans at March 31, 2016 reflects the impact of the transfer of certain residential mortgage loans with a carrying value of $345 million to held for sale during the first quarter of 2016.

[3] The decrease in past due loans at March 31, 2016 reflects the impact of the transfer of certain residential mortgage loans with a carrying value of $345 million to held for sale during the first quarter of 2016. See Note 6, "Loans Held for Sale," for additional details.