Oman Investment	9 Months Ended
Sep. 30, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Oman Investment	Oman Investment In June of 2012, we entered into a strategic partnership with the Zawawi Group in Oman to establish a mining operation by acquiring 55% of Zawawi Gypsum LLC, or ZGL, which holds the mining rights to a gypsum quarry in Salalah, Oman, for $16 million, including transaction costs. ZGL will develop infrastructure and operate the quarry. Quarry mining operations commenced in October 2013. The second phase of the partnership is a 50/50 manufacturing venture, USG-Zawawi Drywall LLC, or ZDL, with Zawawi Minerals LLC to build and operate a low cost wallboard plant in Oman. The plant site is in close proximity to the gypsum quarry and port facilities, facilitating access to markets in India and the Middle East. We expect to commence wallboard production operations in the third quarter of 2014. We accounted for the acquisition of the mining rights as an asset acquisition and measured our interest in the mining rights at our cost. The mining rights will be depleted based upon tonnage mined relative to the total probable capacity in the quarry, and are presented within total property, plant and equipment in our consolidated balance sheets. We determined that both entities are variable interest entities (VIEs). We believe that we direct the activities that most significantly impact the VIEs through our appointment of the general manager, who oversees both ventures and whose responsibilities include developing infrastructure, operating the quarry and directing the entity's product development and pricing strategies. As such, we consolidate the VIEs and, in June 2012, in conjunction with the acquisition of the mining rights, we established a 45% noncontrolling interest of $13 million within stockholders' equity based upon the fair value of the mining rights, with a corresponding increase to the mining rights. There was no gain or loss recognized upon the initial consolidation of the mining VIE. In January of 2013, under our strategic partnership agreement, we paid an additional $17 million to obtain additional mining rights. Concurrently, our joint venture partner who holds the noncontrolling interest contributed its share of the mining rights. Based upon the fair value of the mining rights, the noncontrolling interest within stockholders' equity increased by $13 million and the mining rights, reflected within property, plant and equipment, increased by $30 million. During the first nine months of 2013, our joint venture partner provided loans of approximately $3 million to ZDL, which are included in other liabilities in our accompanying consolidated balance sheet as of September 30, 2013. Including these loans, other liabilities includes, in the aggregate, loans payable to our joint venture partner of approximately $7.5 million and $4 million as of September 30, 2013 and December 31, 2012, respectively. During the first nine months of 2013, we provided loans of approximately $3 million to ZDL. Including these loans, we have provided $5 million of loans to ZDL and $3 million of loans to ZGL. Loans we make to these ventures are not reflected on our accompanying consolidated balance sheets because they are eliminated in consolidation. See Note 7 for a description of the credit facilities entered into by our joint ventures in Oman in June 2013. See Note 19 for a description of certain joint venture agreements we entered into in October 2013 in connection with our planned establishment of the USG Boral Joint Venture. As part of the consideration for the USG Boral Joint Venture transaction, we would contribute to the USG Boral Joint Venture our investment in our Oman joint ventures.

Oman Investment

In June of 2012, we entered into a strategic partnership with the Zawawi Group in Oman to establish a mining operation by acquiring 55% of Zawawi Gypsum LLC, or ZGL, which holds the mining rights to a gypsum quarry in Salalah, Oman, for $16 million, including transaction costs. ZGL will develop infrastructure and operate the quarry. Quarry mining operations commenced in October 2013.

The second phase of the partnership is a 50/50 manufacturing venture, USG-Zawawi Drywall LLC, or ZDL, with Zawawi Minerals LLC to build and operate a low cost wallboard plant in Oman. The plant site is in close proximity to the gypsum quarry and port facilities, facilitating access to markets in India and the Middle East. We expect to commence wallboard production operations in the third quarter of 2014.

We accounted for the acquisition of the mining rights as an asset acquisition and measured our interest in the mining rights at our cost. The mining rights will be depleted based upon tonnage mined relative to the total probable capacity in the quarry, and are presented within total property, plant and equipment in our consolidated balance sheets.

We determined that both entities are variable interest entities (VIEs). We believe that we direct the activities that most significantly impact the VIEs through our appointment of the general manager, who oversees both ventures and whose responsibilities include developing infrastructure, operating the quarry and directing the entity's product development and pricing strategies. As such, we consolidate the VIEs and, in June 2012, in conjunction with the acquisition of the mining rights, we established a 45% noncontrolling interest of $13 million within stockholders' equity based upon the fair value of the mining rights, with a corresponding increase to the mining rights. There was no gain or loss recognized upon the initial consolidation of the mining VIE.

In January of 2013, under our strategic partnership agreement, we paid an additional $17 million to obtain additional mining rights. Concurrently, our joint venture partner who holds the noncontrolling interest contributed its share of the mining rights. Based upon the fair value of the mining rights, the noncontrolling interest within stockholders' equity increased by $13 million and the mining rights, reflected within property, plant and equipment, increased by $30 million.

During the first nine months of 2013, our joint venture partner provided loans of approximately $3 million to ZDL, which are included in other liabilities in our accompanying consolidated balance sheet as of September 30, 2013. Including these loans, other liabilities includes, in the aggregate, loans payable to our joint venture partner of approximately $7.5 million and $4 million as of September 30, 2013 and December 31, 2012, respectively.

During the first nine months of 2013, we provided loans of approximately $3 million to ZDL. Including these loans, we have provided $5 million of loans to ZDL and $3 million of loans to ZGL. Loans we make to these ventures are not reflected on our accompanying consolidated balance sheets because they are eliminated in consolidation.

See Note 7 for a description of the credit facilities entered into by our joint ventures in Oman in June 2013.

See Note 19 for a description of certain joint venture agreements we entered into in October 2013 in connection with our planned establishment of the USG Boral Joint Venture. As part of the consideration for the USG Boral Joint Venture transaction, we would contribute to the USG Boral Joint Venture our investment in our Oman joint ventures.