Loans Held for Sale - Additional Information (Details) - USD ($)		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		$ 1,369,000,000		$ 1,369,000,000	$ 2,185,000,000
Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		901,000,000		901,000,000	2,095,000,000
Valuation allowance		50,000,000		50,000,000	21,000,000
Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		468,000,000		468,000,000	90,000,000
Valuation allowance		55,000,000		55,000,000	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		867,000,000		867,000,000	151,000,000
Global Banking [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		901,000,000		901,000,000	200,000,000
Transfer of loans to held-for-sale			$ 1,088,000,000
Lower of amortized cost or fair value adjustment			$ 0
Global Banking - Term Loan Facility [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		763,000,000		763,000,000
Commercial Real Estate [Member] | Commercial Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial real estate loans sold during the period		1,161,000,000
Loss on sale of real estate loans held for sale		(3,000,000)
Loans transferred to held for investment		612,000,000
Total loans held for sale		0		0	1,895,000,000
Residential Mortgage [Member] | Consumer Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans held for sale		391,000,000		391,000,000	11,000,000
Unpaid principal balance of loans transferred to held-for-sale	[1]	27,000,000		524,000,000
Transfer of loans to held-for-sale	[1]	25,000,000		433,000,000
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	$ 3,000,000
Other Income [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Lower of amortized cost or fair value adjustment		5,000,000		38,000,000
Additional lower of amortized cost or fair value adjustment		6,000,000		6,000,000
Other Income [Member] | Global Banking [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Lower of amortized cost or fair value adjustment		$ 4,000,000		$ 30,000,000

[1] 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.