Loans Held for Sale - Additional Information (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2016	Jun. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		$ 1,791			$ 1,791		$ 2,185
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		741			741		2,095
Valuation allowance		54			54		21
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		1,050			1,050		90
Valuation allowance		60			60		13
Commercial Loans - Fair Value Option [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		649			649		151
Global Banking - Loans Transferred to Held for Sale [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		92			92		49
Global Banking [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		741			741		200
Commercial Real Estate [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial real estate loans sold during the period			$ 1,161
Loss on sale of real estate loans held for sale			3
Loans transferred to held for investment			$ 612
Total loans held for sale		0			0		1,895
Residential Mortgage [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		971			971		11
Unpaid principal balance of loans transferred to held-for-sale	[1]	25			549
Transfer of loans to held-for-sale	[1]	23			456
Residential Mortgage And Home Equity Mortgage [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unpaid principal balance of loans transferred to held-for-sale	[1]	648
Transfer of loans to held-for-sale	[1]	628
Subprime [Member] | Residential Mortgage [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		3			3		$ 3
Other Income [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Lower of amortized cost or fair value adjustment attributed to non-credit factors		4			42
Additional lower of amortized cost or fair value adjustment		2			8
Other Income [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Lower of amortized cost or fair value adjustment attributed to non-credit factors		7		$ 2	$ 37	$ 16
Lower of amortized cost or fair value adjustment attributed to non-credit factors, out of period adjustment		7
Provision for Credit Losses [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Lower of cost or fair value adjustment attributed to credit factors		$ 11

[1] 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.