Financial Statements of HSBC USA Inc. (Parent) Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Net income (loss)	$ (37)	$ 33	$ (21)	$ 154	$ (125)	$ 204	$ 87	$ 164	$ 129	$ 330	$ 354
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization									60	59	58
Net change in other assets and liabilities									1,726	386	180
Net change in trading assets and liabilities									(2,312)	3,298	5,091
Net cash provided by (used in) operating activities									(3)	4,651	5,950
Cash flows from investing activities
Net change in loans									7,391	(7,145)	(11,416)
Other, net									111	(386)	34
Net cash used in investing activities									(14,102)	(9,523)	(7,319)
Cash flows from financing activities
Net change in short-term borrowings									110	(7,806)	(6,340)
Issuance of long-term debt, net of issuance costs									8,694	16,586	8,067
Repayment of long-term debt									(4,869)	(9,937)	(3,686)
Preferred stock issuance									1,265	0	0
Preferred stock redemption									(1,265)	(300)	0
Capital contribution from parent									0	4,000	0
Other decreases in capital surplus									(21)	(1)	4
Dividends paid									(67)	(65)	(73)
Net cash provided by financing activities									14,372	4,949	1,299
Net change in cash and due from banks									267	77	(70)
Cash and due from banks at beginning of period				968				891	968	891	961
Cash and due from banks at end of period	1,235				968				1,235	968	891
Cash paid for:
Interest									1,446	942	752
HSBC USA Inc [Member]
Condensed Financial Statements, Captions [Line Items]
Net income (loss)									129	330	354
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization									14	25	4
Net change in other assets and liabilities									274	517	(460)
Undistributed loss (gain) of subsidiaries									(7)	(308)	(556)
Net change in trading assets and liabilities									0	0	624
Other, net									(4)	(31)	(36)
Net cash provided by (used in) operating activities									406	533	(70)
Cash flows from investing activities
Purchases of securities									0	(56)	0
Sales and maturities of securities									254	298	21
Net change in loans									0	0	26
Net change in investments in and receivables due from subsidiaries									(496)	(4,489)	(6,003)
Net change in receivables from other HSBC affiliates									887	835	(764)
Other, net									(27)	(38)	0
Net cash used in investing activities									618	(3,450)	(6,720)
Cash flows from financing activities
Net change in payables to other HSBC affiliates									19	0	0
Net change in short-term borrowings									(727)	(2,794)	1,393
Issuance of long-term debt, net of issuance costs									3,587	11,946	8,013
Repayment of long-term debt									(3,815)	(9,870)	(2,554)
Preferred stock issuance									1,265	0	0
Preferred stock redemption									(1,265)	(300)	0
Capital contribution from parent									0	4,000	0
Other decreases in capital surplus									(21)	(1)	4
Dividends paid									(67)	(65)	(73)
Net cash provided by financing activities									(1,024)	2,916	6,783
Net change in cash and due from banks									0	(1)	(7)
Cash and due from banks at beginning of period				$ 0				$ 1	0	1	8
Cash and due from banks at end of period	$ 0				$ 0				0	0	1
Cash paid for:
Interest									$ 517	$ 406	$ 363