Segment Information (Details) - Reconciliation of Segment EBITDA to Net Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting Information [Line Items]
Net loss attributable to Hexion Inc.	$ (18)	$ (70)	$ (53)	$ (146)
Net income attributable to noncontrolling interest	0	0	(1)	0
Net loss	(18)	(70)	(52)	(146)
Income tax expense	6	9	17	16
Interest expense, net	83	82	250	247
Depreciation and amortization	27	29	85	85
EBITDA	100	64	302	216
Other Asset Impairment Charges	7	13	32	13
Restructuring and Related Cost, Accelerated Depreciation	2	14	2	14
Business realignment costs	5	10	19	27
Gain on disposition	0	0	44	0
Realized and unrealized foreign currency losses (gains)	4	(5)	26	(7)
Loss on extinguishment of debt	0	0	0	3
Other	12	14	39	39
Total adjustments	28	32	72	75
Segment EBITDA	128	96	374	291
Epoxy, Phenolic and Coating Resins
Segment Reporting Information [Line Items]
Segment EBITDA	66	45	208	143
Forest Products Resins
Segment Reporting Information [Line Items]
Segment EBITDA	76	66	219	195
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Segment EBITDA	$ (14)	$ (15)	$ (53)	$ (47)