Segment Information (Details) - Reconciliation of Segment EBITDA to Net Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Segment Reporting Information [Line Items]
Reorganization Items	$ 156	$ 0	$ 156	$ 0
Net loss attributable to Hexion Inc.	(108)	(22)	(160)	(35)
Net income attributable to noncontrolling interest	(1)	(1)	(1)	(1)
Net loss	(107)	(21)	(159)	(34)
Income tax expense	8	3	15	11	$ 40
Interest expense, net	9	84	89	167
Depreciation and amortization	26	28	52	58
EBITDA	(64)	94	(3)	202
Other Asset Impairment Charges	0	0	0	25
Business realignment costs	11	5	15	14
Gain on disposition	0	0	0	44
Professional Fees	3	3	26	6
Realized and unrealized foreign currency (gains) losses	(7)	15	(6)	22
Other	13	11	27	21
Total adjustments	176	34	218	44
Segment EBITDA	112	128	215	246
Epoxy, Phenolic and Coating Resins
Segment Reporting Information [Line Items]
Segment EBITDA	59	72	111	142
Forest Products Resins
Segment Reporting Information [Line Items]
Segment EBITDA	66	76	134	143
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Segment EBITDA	$ (13)	$ (20)	$ (30)	$ (39)