Guarantor Non-Guarantor Subsidiary Financial Information (Details) - Consolidating Statement of Operations - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Net sales	$ 886	$ 946
Cost of sales	750	789
Gross profit	136	157
Selling, general and administrative expense	91	82
Gain on disposition	0	(44)
Asset impairments	0	25
Business realignment costs	(4)	(9)
Other operating expense, net	8	9
Operating income	33	76
Interest expense, net	80	83
Intercompany interest (income) expense, net	0	0
Other non-operating income, net	(1)	(1)
(Loss) income before tax and earnings from unconsolidated entities	46	6
Income tax expense	7	8	$ 40
Loss before earnings from unconsolidated entities	(53)	(14)
Earnings from unconsolidated entities, net of taxes	1	1
Net loss	(52)	(13)
Comprehensive (loss) income attributable to Hexion Inc.	(52)	1
Hexion Inc. [Member]
Net sales	404	431
Cost of sales	341	357
Gross profit	63	74
Selling, general and administrative expense	51	36
Gain on disposition		(24)
Asset impairments		25
Business realignment costs	(2)	(6)
Other operating expense, net	7	0
Operating income	3	31
Interest expense, net	76	79
Intercompany interest (income) expense, net	(20)	(20)
Other non-operating income, net	18	(19)
(Loss) income before tax and earnings from unconsolidated entities	71	9
Income tax expense	0	(7)
Loss before earnings from unconsolidated entities	(71)	(2)
Earnings from unconsolidated entities, net of taxes	19	(11)
Net loss	(52)	(13)
Comprehensive (loss) income attributable to Hexion Inc.	(52)	1
Combined Subsidiary Guarantors [Member]
Net sales	0	0
Cost of sales	0	0
Gross profit	0	0
Selling, general and administrative expense	0	0
Gain on disposition		0
Asset impairments		0
Business realignment costs	0	0
Other operating expense, net	0	0
Operating income	0	0
Interest expense, net	0	0
Intercompany interest (income) expense, net	0	0
Other non-operating income, net	0	0
(Loss) income before tax and earnings from unconsolidated entities	0	0
Income tax expense	0	0
Loss before earnings from unconsolidated entities	0	0
Earnings from unconsolidated entities, net of taxes	12	(3)
Net loss	12	(3)
Comprehensive (loss) income attributable to Hexion Inc.	12	(2)
Combined Non-Guarantor Subsidiaries [Member]
Net sales	531	570
Cost of sales	458	487
Gross profit	73	83
Selling, general and administrative expense	40	46
Gain on disposition		(20)
Asset impairments		0
Business realignment costs	(2)	(3)
Other operating expense, net	1	9
Operating income	30	45
Interest expense, net	4	4
Intercompany interest (income) expense, net	20	20
Other non-operating income, net	(19)	18
(Loss) income before tax and earnings from unconsolidated entities	(25)	(3)
Income tax expense	7	15
Loss before earnings from unconsolidated entities	18	(12)
Earnings from unconsolidated entities, net of taxes	1	1
Net loss	19	(11)
Comprehensive (loss) income attributable to Hexion Inc.	19	2
Consolidation, Eliminations [Member]
Net sales	(49)	(55)
Cost of sales	(49)	(55)
Gross profit	0	0
Selling, general and administrative expense	0	0
Gain on disposition		0
Asset impairments		0
Business realignment costs	0	0
Other operating expense, net	0	0
Operating income	0	0
Interest expense, net	0	0
Intercompany interest (income) expense, net	0	0
Other non-operating income, net	0	0
(Loss) income before tax and earnings from unconsolidated entities	0	0
Income tax expense	0	0
Loss before earnings from unconsolidated entities	0	0
Earnings from unconsolidated entities, net of taxes	(31)	14
Net loss	(31)	14
Comprehensive (loss) income attributable to Hexion Inc.	$ (31)	$ 0