According to the report, Lester, who will be introduced by the team on Monday, will receive half of his signing bonus by April 1.
He will receive the rest of the signing bonus in three installments: with $2.5 million payments due by Dec. 31 in both 2018 and 2019, and a $10 million installment by Sept. 15, 2020.
His contract also includes an option for the 2021 season.
Lester, 30, is a three-time All-Star who helped the Boston Red Sox win two World Series titles in 2007 and 2013. He was traded by Boston to the Oakland Athletics at last season's trading deadline. He went 16-11 with a 2.46 ERA and 220 strikeouts in 2014.
- Scooby Axson