IntercontinentalExchange Inc., the 12-year-old energy and commodity futures bourse, agreed to acquire NYSE Euronext for cash and stock worth $8.2 billion, moving to take control of the world's biggest equities market.

ICE, based in Atlanta, will pay $33.12 a share for the owner of the New York Stock Exchange, 38 percent above yesterday's closing price, according to a statement today. Both boards approved the proposal and the companies expect to complete the transaction in the second half of 2013. Last year, the U.S. Justice Department blocked a joint hostile bid by ICE and Nasdaq OMX Group Inc. for the New York-based company on concern the combination would dominate U.S. stock listings.

Merging NYSE Euronext, which owns the biggest exchanges by value of listings in the U.S., France and the Netherlands, with the second-largest futures market underscores both the growing importance of derivatives and the diminishing influence of the 220-year-old NYSE. The Big Board, once the benchmark for global free markets, has seen its share of trading in stocks listed on the exchange decline to 21 percent from 82 percent.