Financial Statements of HSBC USA Inc. (Parent) Statement of Cash Flows (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2021		Dec. 31, 2020		Dec. 31, 2019
Condensed Financial Statements, Captions [Line Items]
Net income (loss)		$ 688		$ (940)		$ 113
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization		22		34		43
Net change in other assets and liabilities		172		(839)		1,846
Net cash provided by (used in) operating activities		1,820		3,282		(4,259)
Proceeds from Sale and Maturity of Held-to-maturity Securities		1		0		0
Cash flows from investing activities
Other, net		103		(248)		119
Net cash provided by (used in) investing activities		35,072		(10,805)		(8,429)
Cash flows from financing activities
Net change in short-term borrowings		1,386		1,293		(535)
Issuance of long-term debt		7,711		8,487		4,686
Repayment of long-term debt		(10,044)		(10,427)		(10,705)
Return of capital to parent		(1,000)		0		(2,400)
Other increases (decreases) in capital surplus		(4)		10		0
Dividends paid		(77)		(77)		(77)
Net cash provided by (used in) financing activities		(4,135)		19,396		(744)
Net change in cash and due from banks and interest bearing deposits with banks		32,757		11,873		(13,432)
Cash and due from banks and interest bearing deposits with banks at beginning of period		15,655	[1]	3,782	[1]	17,214
Cash and due from banks and interest bearing deposits with banks at end of period	[1]	48,412		15,655		3,782
Cash paid for:
Interest		606		1,518		2,921
HSBC USA
Condensed Financial Statements, Captions [Line Items]
Net income (loss)		688		(940)		113
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization		1		2		5
Net change in other assets and liabilities		(313)		256		1,463
Undistributed loss (gain) of subsidiaries		(702)		897		(205)
Other, net		(4)		(2)		4
Net cash provided by (used in) operating activities		(330)		213		1,380
Cash flows from investing activities
Net change in investments in and receivables due from subsidiaries		2,713		(552)		3,929
Net change in receivables from other HSBC affiliates		(1,345)		1,056		183
Other, net		0		0		1
Net cash provided by (used in) investing activities		1,369		504		4,113
Cash flows from financing activities
Net change in payables to other HSBC affiliates		13		(1)		4
Net change in short-term borrowings		(815)		3,522		(56)
Issuance of long-term debt		6,844		3,394		2,931
Repayment of long-term debt		(6,000)		(7,565)		(5,897)
Return of capital to parent		(1,000)		0		(2,400)
Other increases (decreases) in capital surplus		(4)		10		0
Dividends paid		(77)		(77)		(77)
Net cash provided by (used in) financing activities		(1,039)		(717)		(5,495)
Net change in cash and due from banks and interest bearing deposits with banks		0		0		(2)
Cash and due from banks and interest bearing deposits with banks at beginning of period		0		0		2
Cash and due from banks and interest bearing deposits with banks at end of period		0		0		0
Cash paid for:
Interest		$ 167		$ 379		$ 662

[1] Includes $58 million of cash which is reported in other branch related assets held for sale on the consolidated balance sheet at December 31, 2021.