Global shares gain on strong U.S. GDP data, oil steadies

By Sam Forgione NEW YORK (Reuters) - U.S. and European shares rose on Tuesday, with the Dow industrials topping 18,000 for the first time after an unexpectedly strong report on U.S. economic growth supported risk appetite and eased concerns about falling oil prices. Both the Dow and the S&P 500 hit intraday record highs after the Commerce Department said the final estimate of U.S. gross domestic product for the third quarter was revised up to a 5 percent annual pace, its quickest in 11 years