DISCONTINUED OPERATIONS - Major Classes of Line Items in Income From Discontinued Operations (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2025	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Goodwill impairments		$ 485	$ 425	$ 0
Other operating expense (income), net		(206)	(12)	(28)
Operating income (loss)		(308)	14	707
Interest expense, net		238	341	439
Other (income) expense, net		(41)	(38)	26
Income (loss) from discontinued operations, net of tax		(57)	(312)	2,482
Less: Net income attributable to noncontrolling interest included in discontinued operations		0	11	7
Net income (loss) attributable to Baxter stockholders included in discontinued operations		(57)	(323)	2,475
Discontinued Operations, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net sales		352	4,513	4,922
Cost of sales		226	2,812	3,844
Gross margin		126	1,701	1,078
Selling, general and administrative expenses		116	1,203	1,038
Research and development expenses		16	181	150
Goodwill impairments		0	430	0
Other operating expense (income), net		0	(1)	0
Operating income (loss)		(6)	(112)	(110)
Interest expense, net		13	13	2
Other (income) expense, net		7	10	26
Income (loss) from discontinued operations before gain on disposition and income taxes		(26)	(135)	(138)
Gain on disposition	$ 97	97	0	2,882
Income tax expense (benefit)		128	177	262
Income (loss) from discontinued operations, net of tax		(57)	(312)	2,482
Less: Net income attributable to noncontrolling interest included in discontinued operations		0	11	7
Net income (loss) attributable to Baxter stockholders included in discontinued operations		(57)	(323)	2,475
Discontinued Operations, Disposed of by Sale | Kidney Care
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net sales		352	4,513	4,453
Cost of sales		226	2,812	3,628
Gross margin		126	1,701	825
Selling, general and administrative expenses		116	1,203	993
Research and development expenses		16	181	149
Goodwill impairments		0	430	0
Other operating expense (income), net		0	(1)	0
Operating income (loss)		(6)	(112)	(317)
Interest expense, net		13	13	3
Other (income) expense, net		7	10	25
Income (loss) from discontinued operations before gain on disposition and income taxes		(26)	(135)	(345)
Gain on disposition		97	0	0
Income tax expense (benefit)		128	177	(95)
Income (loss) from discontinued operations, net of tax		(57)	(312)	(250)
Less: Net income attributable to noncontrolling interest included in discontinued operations		0	11	7
Net income (loss) attributable to Baxter stockholders included in discontinued operations		(57)	(323)	(257)
Discontinued Operations, Disposed of by Sale | BioPharma Solutions
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net sales		0	0	469
Cost of sales		0	0	216
Gross margin		0	0	253
Selling, general and administrative expenses		0	0	45
Research and development expenses		0	0	1
Goodwill impairments		0	0	0
Other operating expense (income), net		0	0	0
Operating income (loss)		0	0	207
Interest expense, net		0	0	(1)
Other (income) expense, net		0	0	1
Income (loss) from discontinued operations before gain on disposition and income taxes		0	0	207
Gain on disposition		0	0	2,882
Income tax expense (benefit)		0	0	357
Income (loss) from discontinued operations, net of tax		0	0	2,732
Less: Net income attributable to noncontrolling interest included in discontinued operations		0	0	0
Net income (loss) attributable to Baxter stockholders included in discontinued operations		$ 0	$ 0	$ 2,732