Guarantor Non-Guarantor Subsidiary Financial Information (Details) - Consolidating Balance Sheets - USD ($) $ in Millions	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents (including restricted cash of $0 and $16, respectively)	$ 137		$ 115	$ 118	$ 196
Accounts receivable, net	463		462
Intercompany accounts receivable	0		0
Intercompany loans receivable—current portion	0		0
Finished and in-process goods	291		221
Raw materials and supplies	105		92
Current assets held for sale	0		6
Other current assets	62	$ 56	44
Total current assets	(1,058)		(940)
Investment in unconsolidated entities	19		20
Deferred income taxes	9		8
Long-term assets held for sale	0		2
Other assets, net	40		49
Intercompany loans receivable	0		0
Property and equipment, net	843		924
Goodwill	109		112
Other intangible assets, net	29		42
Total assets	2,107		2,097
Current liabilities
Accounts payable	391		402
Intercompany accounts payable	0		0
Debt payable within one year	84		125
Intercompany loans payable within one year	0		0
Interest payable	101		82
Income taxes payable	7		12
Accrued payroll and incentive compensation	63		47
Current liabilities associated with assets held for sale	0		2
Other current liabilities	111		135
Total current liabilities	757		805
Long-term liabilities
Long-term debt	3,710		3,584
Intercompany loans payable	0		0
Accumulated losses of unconsolidated subsidiaries in excess of investment	0		0
Long-term pension and post employment benefit obligations	247		262
Deferred income taxes	12		11
Other long-term liabilities	182		177
Total liabilities	4,908		4,839
Total Hexion Inc. shareholder’s deficit	(2,801)		(2,741)
Noncontrolling interest	0		(1)
Total deficit	(2,801)		(2,742)
Total liabilities and deficit	2,107		2,097
Hexion Inc. [Member]
Current assets
Cash and cash equivalents (including restricted cash of $0 and $16, respectively)	34		13	6	28
Accounts receivable, net	120		126
Intercompany accounts receivable	64		121
Intercompany loans receivable—current portion	69		1
Finished and in-process goods	123		85
Raw materials and supplies	43		36
Current assets held for sale			1
Other current assets	28		19
Total current assets	(481)		(402)
Investment in unconsolidated entities	144		158
Deferred income taxes	0		0
Long-term assets held for sale			0
Other assets, net	13		17
Intercompany loans receivable	1,121		1,114
Property and equipment, net	365		410
Goodwill	52		52
Other intangible assets, net	21		32
Total assets	2,197		2,185
Current liabilities
Accounts payable	117		129
Intercompany accounts payable	49		80
Debt payable within one year	13		10
Intercompany loans payable within one year	0		22
Interest payable	99		80
Income taxes payable	4		6
Accrued payroll and incentive compensation	29		22
Current liabilities associated with assets held for sale			0
Other current liabilities	62		70
Total current liabilities	373		419
Long-term liabilities
Long-term debt	3,536		3,507
Intercompany loans payable	135		190
Accumulated losses of unconsolidated subsidiaries in excess of investment	812		668
Long-term pension and post employment benefit obligations	28		31
Deferred income taxes	2		2
Other long-term liabilities	112		109
Total liabilities	4,998		4,926
Total Hexion Inc. shareholder’s deficit			(2,741)
Noncontrolling interest			0
Total deficit	(2,801)		(2,741)
Total liabilities and deficit	2,197		2,185
Combined Subsidiary Guarantors [Member]
Current assets
Cash and cash equivalents (including restricted cash of $0 and $16, respectively)	1		0	0	0
Accounts receivable, net	1		1
Intercompany accounts receivable	0		0
Intercompany loans receivable—current portion	0		0
Finished and in-process goods	0		0
Raw materials and supplies	0		0
Current assets held for sale			0
Other current assets	0		0
Total current assets	(2)		(1)
Investment in unconsolidated entities	13		13
Deferred income taxes	0		0
Long-term assets held for sale			0
Other assets, net	7		8
Intercompany loans receivable	0		0
Property and equipment, net	0		0
Goodwill	0		0
Other intangible assets, net	0		0
Total assets	22		22
Current liabilities
Accounts payable	1		0
Intercompany accounts payable	0		0
Debt payable within one year	0		0
Intercompany loans payable within one year	0		0
Interest payable	0		0
Income taxes payable	0		0
Accrued payroll and incentive compensation	0		0
Current liabilities associated with assets held for sale			0
Other current liabilities	0		0
Total current liabilities	1		0
Long-term liabilities
Long-term debt	0		0
Intercompany loans payable	0		0
Accumulated losses of unconsolidated subsidiaries in excess of investment	157		171
Long-term pension and post employment benefit obligations	0		0
Deferred income taxes	0		0
Other long-term liabilities	0		0
Total liabilities	158		171
Total Hexion Inc. shareholder’s deficit			(149)
Noncontrolling interest			0
Total deficit	(136)		(149)
Total liabilities and deficit	22		22
Combined Non-Guarantor Subsidiaries [Member]
Current assets
Cash and cash equivalents (including restricted cash of $0 and $16, respectively)	102		102	112	168
Accounts receivable, net	342		335
Intercompany accounts receivable	49		80
Intercompany loans receivable—current portion	0		22
Finished and in-process goods	168		136
Raw materials and supplies	62		56
Current assets held for sale			5
Other current assets	34		25
Total current assets	(757)		(761)
Investment in unconsolidated entities	19		20
Deferred income taxes	9		8
Long-term assets held for sale			2
Other assets, net	20		24
Intercompany loans receivable	135		190
Property and equipment, net	478		514
Goodwill	57		60
Other intangible assets, net	8		10
Total assets	1,483		1,589
Current liabilities
Accounts payable	273		273
Intercompany accounts payable	64		121
Debt payable within one year	71		115
Intercompany loans payable within one year	69		1
Interest payable	2		2
Income taxes payable	3		6
Accrued payroll and incentive compensation	34		25
Current liabilities associated with assets held for sale			2
Other current liabilities	49		65
Total current liabilities	565		610
Long-term liabilities
Long-term debt	174		77
Intercompany loans payable	1,121		1,114
Accumulated losses of unconsolidated subsidiaries in excess of investment	0		0
Long-term pension and post employment benefit obligations	219		231
Deferred income taxes	10		9
Other long-term liabilities	70		68
Total liabilities	2,159		2,109
Total Hexion Inc. shareholder’s deficit			(519)
Noncontrolling interest			(1)
Total deficit	(676)		(520)
Total liabilities and deficit	1,483		1,589
Consolidation, Eliminations [Member]
Current assets
Cash and cash equivalents (including restricted cash of $0 and $16, respectively)	0		0	$ 0	$ 0
Accounts receivable, net	0		0
Intercompany accounts receivable	(113)		(201)
Intercompany loans receivable—current portion	(69)		(23)
Finished and in-process goods	0		0
Raw materials and supplies	0		0
Current assets held for sale			0
Other current assets	0		0
Total current assets	182		224
Investment in unconsolidated entities	(157)		(171)
Deferred income taxes	0		0
Long-term assets held for sale			0
Other assets, net	0		0
Intercompany loans receivable	(1,256)		(1,304)
Property and equipment, net	0		0
Goodwill	0		0
Other intangible assets, net	0		0
Total assets	(1,595)		(1,699)
Current liabilities
Accounts payable	0		0
Intercompany accounts payable	(113)		(201)
Debt payable within one year	0		0
Intercompany loans payable within one year	(69)		(23)
Interest payable	0		0
Income taxes payable	0		0
Accrued payroll and incentive compensation	0		0
Current liabilities associated with assets held for sale			0
Other current liabilities	0		0
Total current liabilities	(182)		(224)
Long-term liabilities
Long-term debt	0		0
Intercompany loans payable	(1,256)		(1,304)
Accumulated losses of unconsolidated subsidiaries in excess of investment	(969)		(839)
Long-term pension and post employment benefit obligations	0		0
Deferred income taxes	0		0
Other long-term liabilities	0		0
Total liabilities	(2,407)		(2,367)
Total Hexion Inc. shareholder’s deficit			668
Noncontrolling interest			0
Total deficit	812		668
Total liabilities and deficit	$ (1,595)		$ (1,699)