Income Taxes Level 4 (Details) - Components of Income Tax Expense (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current [Abstract]
Federal	$ 0us-gaap_CurrentFederalTaxExpenseBenefit	$ 0us-gaap_CurrentFederalTaxExpenseBenefit	$ 0us-gaap_CurrentFederalTaxExpenseBenefit
State and local	2	3	(2)
Foreign	26us-gaap_CurrentForeignTaxExpenseBenefit	24us-gaap_CurrentForeignTaxExpenseBenefit	12us-gaap_CurrentForeignTaxExpenseBenefit
Total current	28us-gaap_CurrentIncomeTaxExpenseBenefit	27us-gaap_CurrentIncomeTaxExpenseBenefit	10us-gaap_CurrentIncomeTaxExpenseBenefit
Deferred [Abstract]
Federal	1	347	(368)
State and local	(1)	11	(8)
Foreign	(6)	(6)	(44)
Total deferred	(6)msc_DeferredTaxBenefit	352msc_DeferredTaxBenefit	(420)msc_DeferredTaxBenefit
Income tax expense (benefit)	$ 22us-gaap_IncomeTaxExpenseBenefit	$ 379us-gaap_IncomeTaxExpenseBenefit	$ (410)us-gaap_IncomeTaxExpenseBenefit
Federal Statutory Income Tax Rate	35.00%

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Amount of current federal tax expense (benefit) pertaining to income (loss) from continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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