Equity Method Investments (Balance Sheet) (Details) (USG Boral Building Products, USD $) In Millions, unless otherwise specified	Dec. 31, 2014
USG Boral Building Products
Schedule of Equity Method Investments [Line Items]
Current assets	$ 446
Non-current assets	989
Current liabilities	245
Long-term debt	46
Equity method investment other noncurrent liabilities	21
Shareholders' equity	1,123
Current portion of long-term debt	35
Equity method investment equity of non-controlling interests	$ 70

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