Pension Plans and Other Postretirement Benefits Pension and Non Pension Plan Assets - Level 4 (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	$ 5	$ 5	$ 4
Document Fiscal Year Focus	2018
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other International Equity	$ 8	11
Debt Securities Fixed Income	9	7
Cash, Money Market and Other	1	1
Pension Benefits Fair Value of Plan Assets	40	42
Pooled Insurance Products with Fixed Income Guarantee	22	23
Other Postretirement Benefits Plan [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Other International Equity	0	0
Debt Securities Fixed Income	0	0
Cash, Money Market and Other	0	0
Pension Benefits Fair Value of Plan Assets	0	0
Pooled Insurance Products with Fixed Income Guarantee	0	0
Other Postretirement Benefits Plan [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Other International Equity	8	11
Debt Securities Fixed Income	9	7
Cash, Money Market and Other	1	1
Pension Benefits Fair Value of Plan Assets	40	42
Pooled Insurance Products with Fixed Income Guarantee	22	23
Other Postretirement Benefits Plan [Member] \| Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Other International Equity	0	0
Debt Securities Fixed Income	0	0
Cash, Money Market and Other	0	0
Pension Benefits Fair Value of Plan Assets	0	0
Pooled Insurance Products with Fixed Income Guarantee	0	0
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Large Cap Equity Funds	33	38
Small mid Cap Equity Funds	11	12
Other International Equity	27	32
Debt Securities Fixed Income	54	52
Cash, Money Market and Other	22	20
Pension Benefits Fair Value of Plan Assets	147	154
Pension Plan [Member] \| Fair Value, Inputs, Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Large Cap Equity Funds	0	0
Small mid Cap Equity Funds	0	0
Other International Equity	0	0
Debt Securities Fixed Income	0	0
Cash, Money Market and Other	0	0
Pension Benefits Fair Value of Plan Assets	0	0
Pension Plan [Member] \| Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Large Cap Equity Funds	33	38
Small mid Cap Equity Funds	11	12
Other International Equity	27	32
Debt Securities Fixed Income	54	52
Cash, Money Market and Other	0	0
Pension Benefits Fair Value of Plan Assets	125	134
Pension Plan [Member] \| Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Large Cap Equity Funds	0	0
Small mid Cap Equity Funds	0	0
Other International Equity	0	0
Debt Securities Fixed Income	0	0
Cash, Money Market and Other	1	0
Pension Benefits Fair Value of Plan Assets	1	0
Pension Plan [Member] \| Fair Value Measured at Net Asset Value Per Share [Member]
Defined Benefit Plan Disclosure [Line Items]
Large Cap Equity Funds	0	0
Small mid Cap Equity Funds	0	0
Other International Equity	0	0
Debt Securities Fixed Income	0	0
Cash, Money Market and Other	21	20
Pension Benefits Fair Value of Plan Assets	21	20
Domestic Plan [Member] \| Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(5)	(5)	(3)
Pension Benefits Fair Value of Plan Assets	$ 0	$ 0	0
Domestic Plan [Member] \| Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage	100.00%	100.00%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	100.00%
Pension Benefits Fair Value of Plan Assets	$ 147	$ 154	122
Domestic Plan [Member] \| Pension Plan [Member] \| Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage	48.00%	53.00%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	48.00%
Domestic Plan [Member] \| Pension Plan [Member] \| Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage	37.00%	34.00%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	32.00%
Domestic Plan [Member] \| Pension Plan [Member] \| Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage	15.00%	13.00%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	20.00%
Foreign Plan [Member] \| Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension Benefits Fair Value of Plan Assets	$ 0	$ 0	0
Foreign Plan [Member] \| Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage	100.00%	100.00%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	100.00%
Pension Benefits Fair Value of Plan Assets	$ 40	$ 42	$ 35
Foreign Plan [Member] \| Pension Plan [Member] \| Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage	20.00%	26.00%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	20.00%
Foreign Plan [Member] \| Pension Plan [Member] \| Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage	21.00%	17.00%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	19.00%
Foreign Plan [Member] \| Pension Plan [Member] \| Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Actual Allocation, Percentage	59.00%	57.00%
Defined Benefit Plan, Plan Assets, Target Allocation, Percentage	61.00%

MPM Holdings Inc. 10-K