MILWAUKEE -- Herb Kohl, a former Democratic U.S. senator from Wisconsin and former owner of the NBA's Milwaukee Bucks, has died. He was 88.

His death Wednesday was announced by Herb Kohl Philanthropies, which did not give a cause but said he died after a brief illness.

Kohl was a popular figure in Wisconsin, purchasing the Bucks in 1985 for $18 million to keep them from leaving town, and spending generously from his fortune on civic and educational causes throughout the state.

He was one of the richest members of the Senate, and the Senate's only professional sports team owner.

"The opportunity I was given to purchase and to keep the team here in Milwaukee is one of the most unique and fortunate experiences I've ever enjoyed," he once said about purchasing the Bucks.

The small-market team was in the middle of its sixth straight winning season when Kohl bought it, and the Bucks went on to post winning records in his first six full seasons as owner. After stumbling through most of the 1990s, the team improved in the late '90s and early 2000s.

In 2006, Kohl was one of eight league owners to ask NBA commissioner David Stern to implement revenue sharing.

Kohl's civic commitments extended well beyond keeping professional basketball in Wisconsin. He donated $25 million to the University of Wisconsin to help fund construction of the Kohl Center, home to the school's basketball and hockey teams. It was the single largest private donation in university history.

Kohl was born in Milwaukee, where he was a childhood friend of Bud Selig, who went on to become commissioner of Major League Baseball. The two roomed together at the University of Wisconsin and remained friends in adulthood.

After receiving his bachelor's degree from the University of Wisconsin in 1956, Kohl went on to earn a master's degree in business administration from Harvard University in 1958, and he served in the Army Reserve from 1958-64. He helped grow the family-owned business, Kohl's grocery and department stores, and served as company president in the 1970s. The corporation was sold in 1979.

Kohl also got into Wisconsin politics in the 1970s, serving as chair of the state Democratic Party from 1975 to 1977.

In 1988, Kohl decided to run for the Senate, following the announcement that Sen. William Proxmire was retiring, and defeated then-state Sen. Susan Engeleiter, the Republican candidate. He won reelection in 1994, 2000 and 2006.

In the Senate, a body renowned for egos, Kohl was an unusual figure. He was quiet and not one to seek credit, yet effective on issues important to the state, especially dairy policy.

"I am a person who does not believe in invective," he once said. "I never go out and look to grab the mike or go in front of the TV camera. When I go to work everyday, I check my ego at the door."

He also used his money to fund his Senate races, allowing to him to portray himself as "nobody's senator but yours."

Kohl also used his own money to fund the Herb Kohl Educational Foundation, which donates money for scholarships and fellowships to students, teachers and schools in Wisconsin.

He never accepted a pay raise in the Senate; he drew a salary of $89,500 every year, the same pay he got when he entered the Senate in 1989, returning the rest to the Treasury Department.

The Associated Press contributed to this report.