Litigation	6 Months Ended
Jun. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
Litigation	Litigation WALLBOARD PRICING LAWSUITS In 2015, USG, our subsidiary United States Gypsum Company, our former subsidiary L&W Supply Corporation, and seven other wallboard manufacturers were named as defendants in a lawsuit filed in federal court in California by twelve homebuilders alleging that since at least September 2011, U.S. wallboard manufacturers conspired to fix and raise the price of gypsum wallboard sold in the United States and to effectuate the alleged conspiracy by ending the practice of providing job quotes on wallboard. The lawsuit was transferred to the United States District Court for the Eastern District of Pennsylvania under the title In re: Domestic Drywall Antitrust Litigation, MDL No. 2437. In the second quarter of 2016, the Court dismissed with prejudice the portions of the homebuilders’ complaint alleging a conspiracy in 2014 and 2015, ruling that there were insufficient factual allegations to allow such a claim to go forward. The homebuilders' claims alleging a conspiracy prior to 2014 have not been dismissed, and the case proceeds as to those claims. USG has agreed to defend and indemnify L&W Supply Corporation with regard to this matter. Beginning in the third quarter of 2013, class action lawsuits making similar allegations with regard to Canada were filed in Quebec, Ontario and British Columbia courts on behalf of purchasers of wallboard in Canada and naming USG, United States Gypsum Company, our Canadian subsidiary CGC Inc., or CGC, and other wallboard manufacturers as defendants. We believe that the cost, if any, of resolving the homebuilders’ lawsuit and Canadian class action litigation will not have a material effect on our results of operations, financial position or cash flows. ENVIRONMENTAL LITIGATION We are involved in environmental cleanups of property that we own or have owned. In addition, we have previously been notified by state and federal environmental protection agencies of possible involvement as one of numerous “potentially responsible parties” in certain Superfund sites in the United States to pay for some part of the cleanup of hazardous waste. In most of these sites, our involvement is expected to be minimal. As of June 30, 2018 and December 31, 2017, we had accruals of $13 million and $17 million, respectively, for our probable and reasonably estimable liability in connection with these matters. Our accruals take into account all known or estimated undiscounted costs associated with these sites, including site investigations and feasibility costs, site cleanup and remediation, certain legal costs, and fines and penalties, if any. However, we continue to review these accruals as additional information becomes available and revise them as appropriate. Based on the information known to us, we believe these environmental matters will not have a material effect on our results of operations, financial position or cash flows.

Litigation

WALLBOARD PRICING LAWSUITS

In 2015, USG, our subsidiary United States Gypsum Company, our former subsidiary L&W Supply Corporation, and seven other wallboard manufacturers were named as defendants in a lawsuit filed in federal court in California by twelve homebuilders alleging that since at least September 2011, U.S. wallboard manufacturers conspired to fix and raise the price of gypsum wallboard sold in the United States and to effectuate the alleged conspiracy by ending the practice of providing job quotes on wallboard. The lawsuit was transferred to the United States District Court for the Eastern District of Pennsylvania under the title In re: Domestic Drywall Antitrust Litigation, MDL No. 2437. In the second quarter of 2016, the Court dismissed with prejudice the portions of the homebuilders’ complaint alleging a conspiracy in 2014 and 2015, ruling that there were insufficient factual allegations to allow such a claim to go forward. The homebuilders' claims alleging a conspiracy prior to 2014 have not been dismissed, and the case proceeds as to those claims. USG has agreed to defend and indemnify L&W Supply Corporation with regard to this matter.

Beginning in the third quarter of 2013, class action lawsuits making similar allegations with regard to Canada were filed in Quebec, Ontario and British Columbia courts on behalf of purchasers of wallboard in Canada and naming USG, United States Gypsum Company, our Canadian subsidiary CGC Inc., or CGC, and other wallboard manufacturers as defendants.

We believe that the cost, if any, of resolving the homebuilders’ lawsuit and Canadian class action litigation will not have a material effect on our results of operations, financial position or cash flows.

ENVIRONMENTAL LITIGATION

We are involved in environmental cleanups of property that we own or have owned. In addition, we have previously been notified by state and federal environmental protection agencies of possible involvement as one of numerous “potentially responsible parties” in certain Superfund sites in the United States to pay for some part of the cleanup of hazardous waste. In most of these sites, our involvement is expected to be minimal. As of June 30, 2018 and December 31, 2017, we had accruals of $13 million and $17 million, respectively, for our probable and reasonably estimable liability in connection with these matters. Our accruals take into account all known or estimated undiscounted costs associated with these sites, including site investigations and feasibility costs, site cleanup and remediation, certain legal costs, and fines and penalties, if any. However, we continue to review these accruals as additional information becomes available and revise them as appropriate. Based on the information known to us, we believe these environmental matters will not have a material effect on our results of operations, financial position or cash flows.