In March 1984, Mobil announced that it had "secretly" agreed to buy the 22 percent, and would offer the company's remaining stockholders the same price, at $45 a share.[9] In March 1984, Superior Oil was in the process of being acquired by Mobil for $5.7 billion.[12][10] At that time the company was the nation's largest independent oil producer.[13] The takeover was completed in September 1984, with Superior, then based in Houston, becoming a wholly owned subsidiary of Mobil.[14] It was the fifth-largest oil merger in history, with the combined companies having over $60 billion in combined sales.[9] Among other changes, in February 1985 it was reported that Mobil was planning on selling an unprofitable Idaho gold mine it had acquired when it purchased Superior.[15]