Loans Held for Sale - Additional Information (Details) - USD ($)		3 Months Ended
		Mar. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		$ 3,468,000,000	$ 2,185,000,000
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		3,004,000,000	2,095,000,000
Valuation allowance		47,000,000	21,000,000
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		464,000,000	90,000,000
Valuation allowance		45,000,000	13,000,000
Commercial Loans - Fair Value Option [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		95,000,000	151,000,000
Global Banking [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		1,194,000,000	200,000,000
Transfer of loans to held-for-sale		1,088,000,000
Lower of amortized cost or fair value adjustment		0
Commercial Real Estate [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value of loans transferred to held-for-sale		1,797,000,000	1,889,000,000
Total loans held for sale		1,797,000,000	1,895,000,000
Lower of amortized cost or fair value adjustment		0
Residential Mortgage [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value of loans transferred to held-for-sale	[1]	408,000,000
Total loans held for sale		385,000,000	11,000,000
Unpaid principal balance of loans transferred to held-for-sale	[1]	497,000,000
Transfer of loans to held-for-sale	[1]	345,000,000
Subprime [Member] | Residential Mortgage [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		3,000,000	$ 3,000,000
Other Income [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Lower of amortized cost or fair value adjustment		33,000,000
Other Income [Member] | Global Banking [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Lower of amortized cost or fair value adjustment		$ 26,000,000

[1] 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.