Segment Information (Details) - Reconciliation of Segment EBITDA to Net Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Net loss attributable to Hexion Inc.	$ (22)	$ (34)	$ (35)	$ (76)
Net income attributable to noncontrolling interest	(1)	0	(1)	0
Net loss	(21)	(34)	(34)	(76)
Income tax expense (benefit)	3	(1)	11	7
Interest expense, net	84	82	167	165
Depreciation and amortization	28	28	58	56
EBITDA	94	75	202	152
Asset impairments	0	0	25	0
Business realignment costs	5	10	14	17
Gain on disposition	0	0	44	0
Realized and unrealized foreign currency losses (gains)	15	(1)	22	(2)
Loss on extinguishment of debt	0	0	0	3
Other	14	16	27	25
Total adjustments	34	25	44	43
Segment EBITDA	128	100	246	195
Epoxy, Phenolic and Coating Resins
Segment Reporting Information [Line Items]
Segment EBITDA	72	46	142	98
Forest Products Resins
Segment Reporting Information [Line Items]
Segment EBITDA	76	68	143	129
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Segment EBITDA	$ (20)	$ (14)	$ (39)	$ (32)