U.S. Sen. Ben Nelson says he’s frustrated by the political rancor splitting Washington, but that isn’t what prompted the Nebraska Democrat to retire from the Senate.

Nelson’s comments came this week as he prepares to leave the office he’s held for 12 years. His last day will be Jan. 3.

Nelson tells The Associated Press he’s most proud of his work in the so-called Gang of 14, a group of seven Democrats and seven Republicans who brokered a deal to avoid a filibuster showdown over judicial nominees. He also noted his work to secure the new U.S. Strategic Command headquarters at Offutt Air Force Base south of Omaha.

Nelson says a plea from one of his four grown children for more of his time led him to leave the Senate.