Guarantor Non-Guarantor Subsidiary Financial Information (Details) - Consolidating Balance Sheets - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents (including restricted cash of $0 and $15, respectively)	$ 111	$ 128	$ 113	$ 115
Accounts receivable, net	496	412
Intercompany accounts receivable	0	0
Intercompany loans receivable—current portion	0	0
Finished and in-process goods	258	240
Raw materials and supplies	94	94
Other current assets	67	57
Total current assets	(1,026)	(931)
Investment in unconsolidated entities	20	19
Deferred income taxes		0
Other assets, net	40	34
Intercompany loans receivable	0	0
Property and equipment, net	824	841
Operating Lease, Right-of-Use Asset	99	0
Goodwill	108	109
Other intangible assets, net	25	27
Total assets	2,142	1,961
Current liabilities
Accounts payable	354	384
Intercompany accounts payable	0	0
Debt payable within one year	3,875	3,716
Intercompany loans payable within one year	0	0
Interest payable	100	82
Income taxes payable	8	5
Accrued payroll and incentive compensation	47	52
Other current liabilities	105	106
Total current liabilities	4,512	4,345
Long-term liabilities
Long-term debt	94	99
Intercompany loans payable	0	0
Accumulated losses of unconsolidated subsidiaries in excess of investment	0	0
Long-term pension and post employment benefit obligations	215	221
Deferred income taxes	15	15
Other long-term liabilities	196	195
Total liabilities	5,108	4,875
Total Hexion Inc. shareholder’s deficit	(2,964)	(2,912)
Noncontrolling interest	(2)	(2)
Total deficit	(2,966)	(2,914)	(2,740)	(2,742)
Total liabilities and deficit	2,142	1,961
Operating Lease, Liability, Current	23	0
Operating Lease, Liability, Noncurrent	76	0
Hexion Inc. [Member]
Current assets
Cash and cash equivalents (including restricted cash of $0 and $15, respectively)	16	20	19	13
Accounts receivable, net	130	98
Intercompany accounts receivable	46	40
Intercompany loans receivable—current portion	44	82
Finished and in-process goods	100	100
Raw materials and supplies	38	36
Other current assets	21	28
Total current assets	(395)	(404)
Investment in unconsolidated entities	121	134
Deferred income taxes		0
Other assets, net	11	10
Intercompany loans receivable	1,132	1,114
Property and equipment, net	355	363
Operating Lease, Right-of-Use Asset	44
Goodwill	52	53
Other intangible assets, net	18	19
Total assets	2,128	2,097
Current liabilities
Accounts payable	96	126
Intercompany accounts payable	56	66
Debt payable within one year	3,589	3,563
Intercompany loans payable within one year	133	101
Interest payable	99	81
Income taxes payable	2	3
Accrued payroll and incentive compensation	12	22
Other current liabilities	64	61
Total current liabilities	4,062	4,023
Long-term liabilities
Long-term debt	50	52
Intercompany loans payable	52	0
Accumulated losses of unconsolidated subsidiaries in excess of investment	734	781
Long-term pension and post employment benefit obligations	33	34
Deferred income taxes	11	2
Other long-term liabilities	117	117
Total liabilities	5,092	5,009
Total Hexion Inc. shareholder’s deficit	(2,964)	(2,912)
Noncontrolling interest	0	0
Total deficit	(2,964)	(2,912)
Total liabilities and deficit	2,128	2,097
Operating Lease, Liability, Current	11
Operating Lease, Liability, Noncurrent	33
Combined Subsidiary Guarantors [Member]
Current assets
Cash and cash equivalents (including restricted cash of $0 and $15, respectively)	0	0	0	0
Accounts receivable, net	0	0
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
Other current assets	0	0
Total current assets	0	0
Investment in unconsolidated entities	14	12
Deferred income taxes		0
Other assets, net	7	7
Intercompany loans receivable	0	0
Property and equipment, net	0	0
Operating Lease, Right-of-Use Asset	0
Goodwill	0	0
Other intangible assets, net	0	0
Total assets	21	19
Current liabilities
Accounts payable	0	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
Other current liabilities	0	0
Total current liabilities	0	0
Long-term liabilities
Long-term debt	0	0
Intercompany loans payable	0	0
Accumulated losses of unconsolidated subsidiaries in excess of investment	135	146
Long-term pension and post employment benefit obligations	0	0
Deferred income taxes	0	0
Other long-term liabilities	0	0
Total liabilities	135	146
Total Hexion Inc. shareholder’s deficit	(114)	(127)
Noncontrolling interest	0	0
Total deficit	(114)	(127)
Total liabilities and deficit	21	19
Operating Lease, Liability, Current	0
Operating Lease, Liability, Noncurrent	0
Combined Non-Guarantor Subsidiaries [Member]
Current assets
Cash and cash equivalents (including restricted cash of $0 and $15, respectively)	95	108	94	102
Accounts receivable, net	366	314
Intercompany accounts receivable	56	66
Intercompany loans receivable—current portion	133	101
Finished and in-process goods	158	140
Raw materials and supplies	56	58
Other current assets	46	29
Total current assets	(910)	(816)
Investment in unconsolidated entities	20	19
Deferred income taxes		0
Other assets, net	22	17
Intercompany loans receivable	52	0
Property and equipment, net	469	478
Operating Lease, Right-of-Use Asset	55
Goodwill	56	56
Other intangible assets, net	7	8
Total assets	1,591	1,394
Current liabilities
Accounts payable	258	258
Intercompany accounts payable	46	40
Debt payable within one year	286	153
Intercompany loans payable within one year	44	82
Interest payable	1	1
Income taxes payable	6	2
Accrued payroll and incentive compensation	35	30
Other current liabilities	41	45
Total current liabilities	729	611
Long-term liabilities
Long-term debt	44	47
Intercompany loans payable	1,132	1,114
Accumulated losses of unconsolidated subsidiaries in excess of investment	0	0
Long-term pension and post employment benefit obligations	182	187
Deferred income taxes	4	13
Other long-term liabilities	79	78
Total liabilities	2,213	2,050
Total Hexion Inc. shareholder’s deficit	(620)	(654)
Noncontrolling interest	(2)	(2)
Total deficit	(622)	(656)
Total liabilities and deficit	1,591	1,394
Operating Lease, Liability, Current	12
Operating Lease, Liability, Noncurrent	43
Consolidation, Eliminations [Member]
Current assets
Cash and cash equivalents (including restricted cash of $0 and $15, respectively)	0	0	$ 0	$ 0
Accounts receivable, net	0	0
Intercompany accounts receivable	(102)	(106)
Intercompany loans receivable—current portion	(177)	(183)
Finished and in-process goods	0	0
Raw materials and supplies	0	0
Other current assets	0	0
Total current assets	279	289
Investment in unconsolidated entities	(135)	(146)
Deferred income taxes		0
Other assets, net	0	0
Intercompany loans receivable	(1,184)	(1,114)
Property and equipment, net	0	0
Operating Lease, Right-of-Use Asset	0
Goodwill	0	0
Other intangible assets, net	0	0
Total assets	(1,598)	(1,549)
Current liabilities
Accounts payable	0	0
Intercompany accounts payable	(102)	(106)
Debt payable within one year	0	0
Intercompany loans payable within one year	(177)	(183)
Interest payable	0	0
Income taxes payable	0	0
Accrued payroll and incentive compensation	0	0
Other current liabilities	0	0
Total current liabilities	(279)	(289)
Long-term liabilities
Long-term debt	0	0
Intercompany loans payable	(1,184)	(1,114)
Accumulated losses of unconsolidated subsidiaries in excess of investment	(869)	(927)
Long-term pension and post employment benefit obligations	0	0
Deferred income taxes	0	0
Other long-term liabilities	0	0
Total liabilities	(2,332)	(2,330)
Total Hexion Inc. shareholder’s deficit	734	781
Noncontrolling interest	0	0
Total deficit	734	781
Total liabilities and deficit	(1,598)	$ (1,549)
Operating Lease, Liability, Current	0
Operating Lease, Liability, Noncurrent	$ 0