Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	6 Months Ended		12 Months Ended
	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2020	Dec. 31, 2018
Other comprehensive (loss) income, net of tax:
Net (loss) income	$ (88)	$ 2,895	$ (230)	$ (163)
Foreign currency translation adjustments	(3)	(8)	(8)	(8)
Unrealized (loss) gain on cash flow hedge	2	0	(18)	0
Loss recognized from pension and postretirement benefits	0	0	0	(2)
Other comprehensive loss	1	8	26	10
Comprehensive (loss) income	(89)	2,887	(256)	(173)
Comprehensive (income) loss attributable to noncontrolling interest	1	1	0	(1)
Comprehensive (loss) income attributable to Hexion Inc.	(90)	2,886	(256)	(172)
Parent [Member]
Other comprehensive (loss) income, net of tax:
Net (loss) income	(89)		(230)
Other comprehensive loss	1		26
Noncontrolling Interest [Member]
Other comprehensive (loss) income, net of tax:
Net (loss) income	1		0
Other comprehensive loss	$ 0	$ 0	$ 0	$ 0