Related Party Transactions - Summary of Related Party Transactions (Details) - USD ($) $ in Millions		Sep. 30, 2019		Dec. 31, 2018		Sep. 30, 2018
Assets:
Cash and due from banks		$ 1,496		$ 1,514
Interest bearing deposits with banks		11,183		15,700
Securities purchased under agreements to resell		8,263		10,168
Trading assets		29,557		21,978
Loans		71,336		68,978		$ 66,756
Other		6,897		6,325
Total assets		184,760	[1]	172,448	[1]	174,002
Liabilities:
Deposits		119,801		110,955		112,090
Trading liabilities		4,047		3,643
Short-term borrowings		8,962		4,180
Long-term debt		29,347		30,628
Other		4,145		2,536
Total liabilities	[1]	166,302		151,942
Affiliated Entity [Member]
Assets:
Cash and due from banks		486		245
Interest bearing deposits with banks		1,484		1,000
Securities purchased under agreements to resell	[2]	1,341		0
Trading assets		98		102
Loans		2,828		2,274
Other	[2]	239		169
Total assets		6,476		3,790
Liabilities:
Deposits		11,543		12,000
Trading liabilities		1,087		349
Short-term borrowings		4,964		638
Long-term debt		7,847		7,845
Other	[2]	284		333
Total liabilities		25,725		21,165
Commercial Loans [Member]
Assets:
Loans		51,317		49,342
Commercial Loans [Member] | Other Commercial [Member]
Assets:
Loans		5,712	[3]	$ 4,765	[3]	3,898
Commercial Loans [Member] | Other Commercial [Member] | Affiliated Entity [Member]
Assets:
Loans		$ 2,828				$ 1,557

[1] The following table summarizes assets and liabilities related to our consolidated variable interest entities ("VIEs") at September 30, 2019 and December 31, 2018 which are consolidated on our balance sheet. Assets and liabilities exclude intercompany balances that eliminate in consolidation. See Note 17, "Variable Interest Entities," for additional information. Assets: Other assets $94 million and $112 million. Total assets $94 million and $112 million respectively. Liabilities: Long-term debt $66 million and $66 million, Interest, taxes and other liabilities $34 million and $37 million. Total liabilities $100 million and $103 million, respectively.

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

[3] See Note 14, "Related Party Transactions," for additional information regarding loans to HSBC affiliates.