Subsequent Events	9 Months Ended
Sep. 30, 2025
Subsequent Events [Abstract]
Subsequent Events	13. SUBSEQUENT EVENTS Agreement to Acquire Southwest Bancshares, Inc. — On October 1, 2025, Bancshares and Southwest Bancshares, Inc. (“Southwest) jointly announced the signing of a definitive merger agreement (the “Prosperity/Southwest Merger Agreement”) whereby Southwest, a Texas corporation and bank holding company of Texas Partners Bank (“Texas Partners”), will merge with and into Bancshares and Texas Partners will merge with and into the Bank (collectively, the “Southwest Merger”). Texas Partners operates eleven banking offices in Central Texas including its main office in San Antonio, and banking offices in the San Antonio area, Austin and the Hill Country. As of June 30, 2025, Southwest, on a consolidated basis, reported total assets of $2.35 billion, total loans of $1.89 billion and total deposits of $2.13 billion. Pursuant to the terms of the Prosperity/Southwest Merger Agreement, Bancshares will issue 4,062,520 shares of its common stock for all outstanding stock and restricted stock awards of Southwest, subject to certain potential adjustments. Southwest warrants and in-the-money Southwest stock options that are outstanding at the closing will be converted into cash payments based on the value of the merger consideration (less the applicable exercise price), as calculated pursuant to the terms of the Prosperity/Southwest Merger Agreement. Based on Bancshares’ closing price of $65.97 on September 29, 2025, the total consideration was valued at approximately $268.9 million. The transaction is subject to customary closing conditions, including the receipt of regulatory approvals and approval by the shareholders of Southwest. The transaction is expected to be completed during the first quarter of 2026.

Subsequent Events

9 Months Ended

Sep. 30, 2025

13. SUBSEQUENT EVENTS

Agreement to Acquire Southwest Bancshares, Inc. — On October 1, 2025, Bancshares and Southwest Bancshares, Inc. (“Southwest) jointly announced the signing of a definitive merger agreement (the “Prosperity/Southwest Merger Agreement”)

whereby Southwest, a Texas corporation and bank holding company of Texas Partners Bank (“Texas Partners”), will merge with and into Bancshares and Texas Partners will merge with and into the Bank (collectively, the “Southwest Merger”). Texas Partners operates eleven banking offices in Central Texas including its main office in San Antonio, and banking offices in the San Antonio area, Austin and the Hill Country. As of June 30, 2025, Southwest, on a consolidated basis, reported total assets of $2.35 billion, total loans of $1.89 billion and total deposits of $2.13 billion.

Pursuant to the terms of the Prosperity/Southwest Merger Agreement, Bancshares will issue 4,062,520 shares of its common stock for all outstanding stock and restricted stock awards of Southwest, subject to certain potential adjustments. Southwest warrants and in-the-money Southwest stock options that are outstanding at the closing will be converted into cash payments based on the value of the merger consideration (less the applicable exercise price), as calculated pursuant to the terms of the Prosperity/Southwest Merger Agreement. Based on Bancshares’ closing price of $65.97 on September 29, 2025, the total consideration was valued at approximately $268.9 million. The transaction is subject to customary closing conditions, including the receipt of regulatory approvals and approval by the shareholders of Southwest. The transaction is expected to be completed during the first quarter of 2026.