Debt Obligations Level 4 (Details) Debt Outstanding - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Synthetic Letter of Credit Facility	$ 47
ABL Facility [Domain]
Debt Instrument [Line Items]
Line of Credit, Current	81
Line of Credit Facility, Remaining Borrowing Capacity	227
Non-Affiliated Debt [Abstract]
Long-term Debt		$ 0
Due Within One Year	0	0
6.625% First Priority Senior Notes Due 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Premium	2	3
Non-Affiliated Debt [Abstract]
Long-term Debt	1,552	1,553
Due Within One Year	0	0
10.00% First Priority Senior Notes Due 2020 [Member]
Non-Affiliated Debt [Abstract]
Long-term Debt	315	315
Due Within One Year	0	0
10.375% First-Priority Senion Secured Notes due 2022 [Member]
Non-Affiliated Debt [Abstract]
Long-term Debt	560	0
Due Within One Year	0	0
8.875% Senior Secured Notes Due 2018 [Member]
Debt Instrument [Line Items]
Debt Instrument, Unamortized Discount	0	1
Non-Affiliated Debt [Abstract]
Long-term Debt	0	706
Due Within One Year	0	0
13.75% Senior Secured Notes due 2022 [Member]
Non-Affiliated Debt [Abstract]
Long-term Debt	225	0
Due Within One Year	0	0
9.00% Second-Priority Senior Secured Notes Due 2020 [Member]
Non-Affiliated Debt [Abstract]
Long-term Debt	574	574
Due Within One Year	0	0
9.2% Debentures Due 2021 [Member]
Non-Affiliated Debt [Abstract]
Long-term Debt	74	74
Due Within One Year	0	0
7.875% Debentures Due 2023 [Member]
Non-Affiliated Debt [Abstract]
Long-term Debt	189	189
Due Within One Year	0	0
Australia Facility Due 2014 [Member]
Non-Affiliated Debt [Abstract]
Long-term Debt	0	0
Due Within One Year	50	51
Affiliated Debt [Abstract]
Line of Credit Facility, Maximum Borrowing Capacity	8
Brazilian Bank Loans [Member]
Non-Affiliated Debt [Abstract]
Long-term Debt	9	14
Due Within One Year	34	26
Capital Leases [Member]
Non-Affiliated Debt [Abstract]
Long-term Debt	44	7
Due Within One Year	5	2
Other [Member]
Non-Affiliated Debt [Abstract]
Long-term Debt	2	3
Due Within One Year	36	28
Unamortized debt issuance costs [Member]
Non-Affiliated Debt [Abstract]
Long-term Debt	(41)	(38)
Unamortized debt issuance costs
Non-Affiliated Debt [Abstract]
Due Within One Year	0	0
Total non-affiliated debt [Member]
Non-Affiliated Debt [Abstract]
Long-term Debt	3,584	3,397
Due Within One Year	$ 125	$ 107

Affiliated Debt [Abstract]

No definition available.

Name:	msc_AffiliatedDebtAbstract
Namespace Prefix:	msc_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Non-Affiliated Debt [Abstract]

+ References

No definition available.

+ Details

Name:	msc_NonAffiliatedDebtAbstract
Namespace Prefix:	msc_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

synthetic letter of credit facility

+ References

No definition available.

+ Details

Name:	msc_SyntheticLetterOfCreditFacility
Namespace Prefix:	msc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, after accumulated amortization, of debt discount.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28541-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentUnamortizedDiscount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, after accumulated amortization, of debt premium.

+ References

+ Details

Name:	us-gaap_DebtInstrumentUnamortizedPremium
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current portion of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(13))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LinesOfCreditCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19,20)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebtCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentAxis=msc_ABLFacilityDomain
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=msc_A6625FirstPrioritySeniorNotesDue2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=msc_A10.00FirstPrioritySeniorNotesDue2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=msc_A10.375FirstPrioritySenionSecuredNotesdue2022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=msc_A8875SeniorSecuredNotesDue2018Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=msc_A13.75SeniorSecuredNotesdue2022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=msc_A900SecondPrioritySeniorSecuredNotesDue2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=msc_A92DebenturesDue2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=msc_A7875DebenturesDue2023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=msc_AustraliaFacilityDue2014Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=msc_BrazilianBankLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_CapitalLeaseObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=us-gaap_UnsecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=msc_UnamortizeddebtissuancecostsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=msc_DeferredIssuanceCostsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=msc_TotalNonAffiliatedDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: