Catherine Zeta-Jones Returns Home from Treatment for Bipolar II Disorder
05/20/2013 AT 09:45 PM EDT
"She comes home tomorrow," he told PEOPLE on Monday. "She's doing a really good job of getting balanced. I'm proud of her."
The actress, 43, entered treatment for the second time in April as Douglas, 68, was beginning to generate praise for his role as the flamboyant piano player and vocalist, Liberace.
Zeta-Jones, for one, is already a fan. "She loves it," says Douglas. "It cracks her up. She thinks it's a great movie."
Costarring Matt Damon as Liberace's lover, the film lent Douglas a new perspective on the legendary performer's lifestyle.
"He was a very hard-working guy who never seemed to lose his cool," he says. "It was a joy playing a nice guy. I don't get to play a lot of nice guys."
Look for much more from PEOPLE's interview with Michael Douglas in an upcoming issue of the magazine