Amount of the Increase or Decrease in the amount of the asset retirement obligation during the current period for changes in the amount or timing of the estimated cash flows associated with the settlement of the obligation.

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Fair Value Measurements (Details Textual) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-lived asset impairment charges	$ 90us-gaap_TangibleAssetImpairmentCharges	$ 30us-gaap_TangibleAssetImpairmentCharges	$ 90us-gaap_TangibleAssetImpairmentCharges	$ 0us-gaap_TangibleAssetImpairmentCharges	$ 8us-gaap_TangibleAssetImpairmentCharges
Increase in related asset retirement obligation			(13)	(11)
Fair value of long-lived assets					6
Other long lived asset impairment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-lived asset impairment charges				0	1
Asset Retirement Obligation Impairment \| Closed Gypsum Quarry and Ship Loading Facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-lived asset impairment					7
Self-unloading ocean vessels
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-lived asset impairment charges	60		60
Closed gypsum quarry and ship loading facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Increase in related asset retirement obligation					$ 7