Financial Statements of HSBC USA Inc. (Parent) Statement of Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income:
Other interest income									$ 82	$ 77	$ 52
Total income									3,771	4,224	4,440
Expenses:
Other Interest Expense									35	36	25
Income before income tax	$ 181	$ (211)	$ 156	$ 144	$ 146	$ 235	$ 351	$ (146)	270	586	1,049
Income tax expense (benefit)	48	39	35	35	34	58	82	92	157	266	1,228
Net income (loss)	$ 133	$ (250)	$ 121	$ 109	$ 112	$ 177	$ 269	$ (238)	113	320	(179)
HSBC USA Inc [Member]
Income:
Dividends from banking subsidiaries									138	137	136
Interest from subsidiaries									350	367	309
Interest from other HSBC affiliates									91	55	37
Other interest income									0	0	5
Other income (loss) from subsidiaries									2	(2)	(1)
Other income (loss) from other HSBC Affiliates									1,645	(829)	1,093
Other income (loss)									(1,690)	792	(772)
Total income									536	520	807
Expenses:
Interest to other HSBC Affiliates									140	62	40
Other Interest Expense									549	574	541
Other expenses with subsidiaries									12	8	15
Other expenses									5	2	3
Total expenses									706	646	599
Income before income tax									(170)	(126)	208
Income tax expense (benefit)									(78)	(66)	18
Income (loss) before equity in undistributed income (loss) of subsidiaries									(92)	(60)	190
Equity in undistributed income (loss) of subsidiaries									205	380	(369)
Net income (loss)									$ 113	$ 320	$ (179)