Segment Information Level 4 (Details) - Reconciliation of Segment EBITDA to Net Income - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Mar. 31, 2017	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Segment EBITDA [Line Items]			$ 365	$ 433	$ 466
Asset impairment Charges	$ 0	$ 13	(13)	0	6
Business realignment costs			52	55	16
Gain on Disposition			0	(240)	0
Asset and goodwill impairment			(13)	0	(6)
Unrealized and realized foreign currency losses excluded from EBITDA			3	(11)	10
Other			56	73	28
Total adjustments			123	(137)	6
Loss (gain) on extinguishment of debt			3	(48)	(41)
Unrealized gains (losses) on pension and OPEB plan liabilities			(4)	34	(13)
Interest expense, net			329	310	326
Income tax expense			18	38	34
Depreciation and amortization			115	131	137
Restructuring and Related Cost, Accelerated Depreciation			14	129	(2)
Earnings before Interest, Taxes, Depreciation, and Amortization			242	570	460
Net loss attributable to Hexion Inc.			(234)	(38)	(40)
Net loss			(234)	(38)	(39)
EPCD [Member]
Segment Reporting Information [Line Items]
Segment EBITDA [Line Items]			174	258	307
Depreciation and amortization			71	87	96
FPD [Member]
Segment Reporting Information [Line Items]
Segment EBITDA [Line Items]			257	240	233
Asset impairment Charges				2
Depreciation and amortization			40	40	35
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Segment EBITDA [Line Items]			(66)	(65)	(74)
Depreciation and amortization			$ 4	$ 4	$ 6