Willis Group to merge with Towers Watson by Claire Groden @FortuneMagazine June 30, 2015, 8:31 AM EDT E-mail Tweet Facebook Google Plus Linkedin Share icons Willis Group Holdings WSH , an insurance broker and risk advisory firm, and professional services group Towers Watson TW , announced Tuesday they plan to merge. The combined company, Willis Towers Watson, will be worth $18 billion, taking in about $8.2 billion in revenue, according to The Wall Street Journal. The Ireland-based company is expected to achieve over $100 million in cost-savings on account of the merger. The Towers Watson Chairman and CEO, John Haley, will remain CEO, and Willis Group Holdings CEO Dominic Casserley will be president and deputy CEO. “These are two companies with world-class brands and shared values. The rationale for the merger is powerful – at one stroke, the combination fast-tracks each company’s growth strategy and offers a truly compelling value proposition to our clients,” said Casserley in a press release. “We will advise over 80% of the world’s top-1000 companies, as well as having a significant presence with mid-market and smaller employers around the world,” he added.