AT&T Inc. is an American multinational telecommunications corporation, headquartered at Whitacre Tower in downtown Dallas, Texas. AT&T is the second-largest provider of mobile telephony and the largest provider of fixed telephony in the United States, and also provides broadband subscription television services. AT&T is the third-largest company in Texas (the largest non-oil company, behind only ExxonMobil and ConocoPhillips, and also the largest Dallas company). As of May 2013, AT&T is the 21st-largest company in the world by market value, and the 13th-largest non-oil company. As of 2014, it is also the 20th-largest mobile telecom operator in the world, with over 250 million mobile customers.