As CEO of the Bob Woodruff Foundation, Anne Marie Dougherty has encountered a lot of high-net-worth individuals and how they approach philanthropy. But few are like MacKenzie Scott, Dougherty told Fortune.

Scott’s signature philanthropic style is giving unrestricted gifts—a rarity in the industry. It means organizations who receive a gift from the billionaire philanthropist, novelist, and ex-wife of Amazon founder Jeff Bezos can use the donation how they see fit. That style contrasts with many other high-profile donors, who put conditions like donation-matching or performance goals around gifts. This can lead to confusion and delays in putting the money to use.

Since 2020, Scott has donated more than $20 billion, making her one of the most generous philanthropists, alongside Bill Gates, Melinda French Gates, and Warren Buffett. According to her foundation, Yield Giving, she’s donated more than $19.25 billion, but that doesn’t even reflect this year’s gifts. This fall alone, she’s donated hundreds of millions of dollars to organizations focused on DEI, education, and disaster recovery.

“She practices trust-based philanthropy,” Dougherty said of Scott, who donated $15 million to the veteran-focused nonprofit organization in 2022, and made a subsequent $20 million donation this fall. The $15 million gift was the largest in history at the organization, which was founded in 2006—the same year military reporter Bob Woodruff was severely injured by a roadside bomb in Iraq. The foundation was cofounded by Woodruff and his family to provide support for injured service members, veterans, and their families.