Equity Method Investments (Statement of Operations) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Equity Method Investments [Line Items]
Income from equity method investments	$ 35	$ 1	$ 0
USG Boral Building Products
Schedule of Equity Method Investments [Line Items]
Net sales	927
Gross profit	251
Net income	72
Income from equity method investments	33
Other equity method investments
Schedule of Equity Method Investments [Line Items]
Income from equity method investments	2	1	0
USG Boral Building Products | USG Boral Building Products
Schedule of Equity Method Investments [Line Items]
Net sales	927
Operating profit	95
Net income from continuing operations	72
Net income attributable to USG Boral Building Products	$ 67