Related Party Transactions - Summary of Related Party Transactions (Details) - USD ($)		Mar. 31, 2017		Dec. 31, 2016		Mar. 31, 2016	Dec. 31, 2015
Assets:
Cash and due from banks		$ 1,037,000,000		$ 1,235,000,000		$ 863,000,000	$ 968,000,000
Interest bearing deposits with banks		17,870,000,000		20,238,000,000
Securities purchased under agreements to resell		30,550,000,000		30,023,000,000
Trading assets		22,823,000,000		16,850,000,000
Loans		69,588,000,000		73,875,000,000		81,732,000,000
Other assets		6,799,000,000		6,755,000,000
Total assets		201,583,000,000	[1]	201,301,000,000	[1]	203,784,000,000
Liabilities:
Deposits		129,258,000,000		129,248,000,000		126,303,000,000
Trading liabilities		4,024,000,000		4,908,000,000
Short-term borrowings		5,438,000,000		5,101,000,000
Long-term debt		37,803,000,000		37,739,000,000
Other		4,386,000,000		3,950,000,000
Total liabilities	[1]	180,909,000,000		180,946,000,000
Hnah [Member]
Related Party Transaction [Line Items]
Maximum borrowing capacity		150,000,000		150,000,000
Long-term Line of Credit		0		0
Liabilities:
Long-term debt		4,900,000,000		4,900,000,000
Affiliated Entity [Member]
Related Party Transaction [Line Items]
Loans and leases receivable from related parties		939,000,000		3,274,000,000
Assets:
Cash and due from banks		233,000,000		364,000,000
Interest bearing deposits with banks		797,000,000		980,000,000
Securities purchased under agreements to resell	[2]	0		949,000,000
Trading assets		30,000,000		74,000,000
Loans		939,000,000		3,274,000,000		$ 5,107,000,000
Other assets	[3]	388,000,000		291,000,000
Total assets		2,387,000,000		5,932,000,000
Liabilities:
Deposits		24,026,000,000		23,999,000,000
Trading liabilities		701,000,000		510,000,000
Short-term borrowings		2,047,000,000		2,148,000,000
Long-term debt		4,836,000,000		4,834,000,000
Other	[3]	333,000,000		247,000,000
Total liabilities		$ 31,943,000,000		$ 31,738,000,000

[1] The following table summarizes assets and liabilities related to our consolidated variable interest entities ("VIEs") at March 31, 2017 and December 31, 2016 which are consolidated on our balance sheet. Assets and liabilities exclude intercompany balances that eliminate in consolidation. See Note 24, "Variable Interest Entities," for additional information. Assets: Other assets $220 million and $231 million. Total assets $220 million and $231 million respectively. Liabilities: Long-term debt $79 million and $79 million, Interest, taxes and other liabilities $54 million and $60 million. Total liabilities $133 million and $139 million, respectively.

[2] Reflects overnight purchases of U.S. Treasury securities which HSBC Securities (USA) Inc. ("HSI") has agreed to repurchase.

[3] Other assets and other liabilities primarily consist of derivative balances associated with hedging activities and other miscellaneous account receivables and payables.