Allowance for Credit Losses - Summary of Changes in Allowance for Credit Losses and Related Loan Balance by Product - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	$ 73,875		$ 82,917	$ 77,741
Allowance for credit losses	1,017		912	680	$ 606
TDR loans carried at lower of amortized cost or fair value less cost to sell	672		881	763
Affiliated Entity [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	3,274		4,815	4,821
Commercial Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	54,216		62,453
Consumer Loans [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans	19,659		20,464
Loans Reclassified to Global Banking [Member] | Commercial Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans			4,800	3,900	3,400
Allowance for credit losses			27	24	7
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
Additional charge-off for the existing allowance for credit losses on collateral dependent loans transferred to held for sale	22
Loans	17,181	[1],[2]	17,758	16,661
Allowance for credit losses	$ 26		$ 68	$ 107	$ 186

[1] The decrease in nonaccrual loans at December 31, 2016 reflects the impact of transfers of certain residential mortgage loans to held for sale during 2016.

[2] The decrease in past due loans at December 31, 2016 reflects the impact of transfers of certain residential mortgage loans to held for sale during 2016. See Note 7, "Loans Held for Sale" for additional details.