Columbia Financial (CLBK) said Tuesday it completed its conversion from a mutual holding company structure and closed its previously announced $580 million acquisition of Northfield Bancorp.

On a pro forma basis as of March 31, the combined company had about $18 billion in assets, $12.5 billion in deposits, $11.9 billion in loans and more than 100 branches across New Jersey, Staten Island and Brooklyn, the company said.

The company said it sold about 167.2 million shares at $10 each in its stock offering, adding that existing public shareholders received 2.2 shares of Columbia Financial common stock for each holding company share.

Under the merger agreement, the company said Northfield shareholders received either $14.25 in cash, 1.425 Columbia shares, or a combination of both, with the final consideration consisting of 70% stock and 30% cash.

Columbia Financial said its shares began trading on the Nasdaq Global Select Market on Tuesday under the ticker 'CLBK'.