Allowance for Credit Losses - Summary of Changes in Allowance for Credit Losses and Related Loan Balance by Product - Additional Information (Detail) - USD ($) $ in Millions	Jun. 30, 2016		Dec. 31, 2015	Jun. 30, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	$ 79,810		$ 82,917	$ 83,617
TDR Loans Carried At Lower Of Amortized Cost Or Fair Value Less Cost To Sell	763		881	775
Affiliated Entity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	5,072		4,815	4,607
Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	20,267		20,464
Residential Mortgage [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	$ 17,667	[1],[2]	$ 17,758	$ 17,233

[1] The decrease in nonaccrual loans at June 30, 2016 reflects the impact of the transfer of certain residential mortgage loans with a carrying value of $369 million to held for sale during the first half of 2016.

[2] The decrease in past due loans at June 30, 2016 reflects the impact of the transfer of certain residential mortgage loans with a carrying value of $369 million to held for sale during the first half of 2016. See Note 6, "Loans Held for Sale," for additional details.