Discontinued Operations Textual (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012
Related Party Transaction [Line Items]
Cash and Cash Equivalents of Disposal Group not Included in Discontinued Operations	$ 37
Pension Plan Benefit Obligation of Disposal Group not Included in Discontinued Operations	1
Approximate Selling Total Price of Disposal Group	$ 80
Knauf [Member]
Related Party Transaction [Line Items]
Disposal Group Purchasers Affiliates Beneficial Ownership in Common Stock of USG	14.00%