TORONTO, Oct 4 (Reuters) - Sun Life Financial (SLF.TO) said it will acquire U.S. dental benefits provider DentaQuest for $2.48 billion in its biggest deal in two decades, becoming the latest cashed-up Canadian insurance company pursuing growth outside its home market. The deal to acquire the United States" second-largest dental benefits provider, with more than 33 million members, will add about $100 million to its U.S. underlying income in its first full-year after closing, executives at Canada"s second-largest life insurer said on an analyst call on Monday. Sun Life announced the deal late on Sunday. It is the biggest acquisition since Sun Life bought Clarica Life Insurance, from where Chief Executive Kevin Strain joined the company, for C$7.3 billion ($5.8 billion) in 2002, according to a spokeswoman.Sun Life shares rose 1.7% to C$66.20 in morning trading in Toronto, compared with a 0.4% decline in the stock benchmark (.GSPTSE). After synergies, expected to be $60 million, the firm is expected to add 24 Canadian cents to underlying earnings per share and 50 basis points to its return on equity, Canaccord Genuity analyst Scott Chan said, adding the transaction is "expected to support Sun Life"s peer-leading ROE metrics." The deal follows a slew of other acquisitions in recent years by Canadian life insurers, who, facing limited growth at home and holding record levels of capital, pursue deals overseas, particularly in the United States recently. Great-West Lifeco was the latest, agreeing in July to pay C$4.45 billion to buy Prudential Financial Inc"s (PRU.N) full-service retirement business. read more Sun Life itself has been expanding in the U.S. group benefits business, albeit with smaller deals, including that of U.S. medical intelligence and health-care navigation provider PinnacleCare and benefits platform Maxwell Health. It had previously flagged an appetite to grow its group benefits and stop-loss business, which protects against unpredictable losses. The deal gives Sun Life the "flexibility to maneuver" in future and make additional investments, particularly as it seeks to expand its pharmacy stop-loss business as well as to take advantage of potential expansions of health care services and funding in the U.S., executives said on the call. Sun Life will incur transaction and integration costs of $250 million, the executives said. ($1 = 1.2562 Canadian dollars)