Structured entities - Nature and risks associated with interests in unconsolidated structured entities (Details) $ in Millions	Dec. 31, 2018 USD ($) entity	Jan. 01, 2018 USD ($)	[1]	Dec. 31, 2017 USD ($) entity	Dec. 31, 2016 USD ($)
Disclosure of unconsolidated structured entities [line items]
– trading assets	$ 238,130	$ 254,410		$ 287,995
– financial assets designated and otherwise mandatorily measured at fair value	41,111	39,746		29,464
– loans and advances to banks	72,167	82,559		90,393
– loans and advances to customers	981,696	$ 949,737		962,964	$ 861,504
– financial investments	13,753			13,128
– other liabilities	$ 19,905			$ 21,202
Total
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	2,301			2,564
Total assets in relation to HSBC’s interests in the unconsolidated structured entities	$ 25,700			$ 26,500
– trading assets	1,700			2,800
– financial assets designated and otherwise mandatorily measured at fair value	15,200			16,300
– loans and advances to banks				100
– loans and advances to customers	6,800			5,100
– financial investments	1,600			1,800
– other assets	400			400
Total liabilities in relation to HSBC’s interests in the unconsolidated structured entities	200			300
– other liabilities	200			300
Other off-balance sheet commitments	5,200			2,600
HSBC's maximum exposure	$ 30,700			$ 29,100
Total | 0–500
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	1,304			1,539
Total | 500–2,000
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	641			643
Total | 2,000–5,000
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	248			252
Total | 5,000–25,000
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	96			117
Total | Over 25,000
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	12			13
Securitisations
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	87			86
Total assets in relation to HSBC’s interests in the unconsolidated structured entities	$ 3,800			$ 4,000
– trading assets	0			0
– financial assets designated and otherwise mandatorily measured at fair value	0			0
– loans and advances to banks				0
– loans and advances to customers	3,800			4,000
– financial investments	0			0
– other assets	0			0
Total liabilities in relation to HSBC’s interests in the unconsolidated structured entities	0			0
– other liabilities	0			0
Other off-balance sheet commitments	800			0
HSBC's maximum exposure	$ 4,600			$ 4,000
Securitisations | 0–500
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	76			78
Securitisations | 500–2,000
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	10			6
Securitisations | 2,000–5,000
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	1			0
Securitisations | 5,000–25,000
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	0			2
Securitisations | Over 25,000
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	0			0
HSBC managed funds
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	323			406
Total assets in relation to HSBC’s interests in the unconsolidated structured entities	$ 8,300			$ 9,100
– trading assets	100			200
– financial assets designated and otherwise mandatorily measured at fair value	7,300			8,000
– loans and advances to banks				0
– loans and advances to customers	0			0
– financial investments	900			900
– other assets	0			0
Total liabilities in relation to HSBC’s interests in the unconsolidated structured entities	0			0
– other liabilities	0			0
Other off-balance sheet commitments	100			100
HSBC's maximum exposure	$ 8,400			$ 9,200
HSBC managed funds | 0–500
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	243			321
HSBC managed funds | 500–2,000
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	56			56
HSBC managed funds | 2,000–5,000
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	17			17
HSBC managed funds | 5,000–25,000
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	5			10
HSBC managed funds | Over 25,000
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	2			2
Non-HSBC managed funds
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	1,806			1,858
Total assets in relation to HSBC’s interests in the unconsolidated structured entities	$ 8,900			$ 9,300
– trading assets	300			200
– financial assets designated and otherwise mandatorily measured at fair value	7,900			8,300
– loans and advances to banks				0
– loans and advances to customers	300			0
– financial investments	400			800
– other assets	0			0
Total liabilities in relation to HSBC’s interests in the unconsolidated structured entities	0			0
– other liabilities	0			0
Other off-balance sheet commitments	3,300			2,200
HSBC's maximum exposure	$ 12,200			$ 11,500
Non-HSBC managed funds | 0–500
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	906			930
Non-HSBC managed funds | 500–2,000
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	570			578
Non-HSBC managed funds | 2,000–5,000
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	230			235
Non-HSBC managed funds | 5,000–25,000
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	90			104
Non-HSBC managed funds | Over 25,000
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	10			11
Other
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	85			214
Total assets in relation to HSBC’s interests in the unconsolidated structured entities	$ 4,700			$ 4,100
– trading assets	1,300			2,400
– financial assets designated and otherwise mandatorily measured at fair value	0			0
– loans and advances to banks				100
– loans and advances to customers	2,700			1,100
– financial investments	300			100
– other assets	400			400
Total liabilities in relation to HSBC’s interests in the unconsolidated structured entities	200			300
– other liabilities	200			300
Other off-balance sheet commitments	1,000			300
HSBC's maximum exposure	$ 5,500			$ 4,400
Other | 0–500
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	79			210
Other | 500–2,000
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	5			3
Other | 2,000–5,000
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	0			0
Other | 5,000–25,000
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	1			1
Other | Over 25,000
Disclosure of unconsolidated structured entities [line items]
Number of entities | entity	0			0

[1] Balances at 1 January 2018 have been prepared in accordance with accounting policies referred to on page 263. 31 December 2017 balances have not been re-presented. Information regarding the effects of adoption of IFRS 9 can be found in Note 37.