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		9 Months Ended
	Sep. 30, 2016		Sep. 30, 2016		Dec. 31, 2015	Sep. 30, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	$ 77,625		$ 77,625		$ 82,917	$ 84,942
TDR loans carried at lower of amortized cost or fair value less cost to sell	662		662		881	858
Affiliated Entity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	4,463		4,463		4,815	5,447
Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	19,593		19,593		20,464
Residential Mortgage [Member] | Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Provision for credit losses and charge-offs related to lower of amortized cost or fair value adjustment attributable to credit factors for loans transferred to held for sale	11		11
Additional charge-off for the existing allowance for credit losses on collateral dependent loans transferred to held for sale	20		22
Loans	$ 17,091	[1],[2]	$ 17,091	[1],[2]	$ 17,758	$ 17,460

[1] The decrease in nonaccrual loans at September 30, 2016 reflects the impact of transfers of certain residential mortgage loans to held for sale during the nine months ended September 30, 2016.

[2] The decrease in past due loans at September 30, 2016 reflects the impact of transfers of certain residential mortgage loans to held for sale during the nine months ended September 30, 2016. See Note 6, "Loans Held for Sale" for additional details.