Wintrust Financial Corporation has signed a definitive agreement to acquire Suburban Illinois Bancorp, the parent company of Illinois-state chartered Suburban Bank & Trust Company (SBT).

Under the terms of the transaction, which is subject to approval by banking regulators and Suburban’s shareholders, Wintrust will pay about $12.5m in cash for all the outstanding shares of Suburban’s common stock.

The acquisition of SBT, headquartered in Elmhurst, will add approximately $470m in assets, around $297m in loans and about $411m in deposits, as of 31 December 2014, to Wintrust.

The deal will close late in the second quarter or early in the third quarter of 2015 and will not have a material effect on Wintrust’s 2015 earnings per share.

Wintrust president and CEO Edward Wehmer said: "This transaction provides a wonderful opportunity to expand into the desirable Elmhurst market in a meaningful way and complement our growing presence in other suburban markets.

"Upon completion of the transaction, several of Wintrust’s community banks will have branches that share market areas with existing Suburban branches. We are in the process of evaluating those overlaps, and expect to combine approximately six branches during the second half of 2015."