Associated Banc-Corp (ASB) said late Thursday it plans to launch a public offering of 11.5 million shares of its common stock.

The underwriters are expected to be granted a 30-day option to purchase an additional 1.73 million shares, the company said.

Proceeds will be used for general corporate purposes, according to the company.

Shares of Associated Banc-Corp were down 4.2% in after-hours activity.