Portland-based Umpqua Holdings Corp. announced late Wednesday that it is buying Spokane-based Sterling Financial Corp. in a $2 billion deal. Umpqua Bank is the largest bank headquartered in Oregon.

Once the takeover is complete, the combined company will operate under the Umpqua Bank name and brand, the companies said. Umpqua Chief Executive Ray Davis will serve as president and CEO. Sterling Chief Executive Greg Seibly will join Umpqua Bank as co-president, along with Cort O’Haver, Umpqua Bank’s co-president.

“We look forward to starting the process of bringing our companies together,” Davis said in a statement.

In a statement Wednesday, the companies said both of their boards of directors had unanimously approved the transaction. The combined company’s new board will have 13 directors — nine from Umpqua’s board and four from Sterling’s. Peggy Fowler, chair of the Umpqua board, will continue in that capacity with the new company.

The acquisition will nearly double Umpqua’s size and reach.

Combined, the banks have $22 billion in assets, $15 billion in loans and $16 billion in deposits. They have 5,000 employees and 394 branches across Oregon, Washington, Idaho, California and Nevada.

On Monday, Umpqua shares jumped more than 5 percent after published reports first linked the two banks in takeover talks. Umpqua closed that session at $17.11 on the Nasdaq stock market, and had slipped slightly over the last two days before closing Thursday at $16.14.