The couple released a joint statement saying, "After a great deal of thought, reflection, discussion and prayer, we came to this decision together. At this time, we are living apart while we work on the future of our relationship."
The statement continues, "We are continuing to parent our four children together. They are the light and center of both of our lives."
The couple adds, "We consider this a private matter and neither we nor any of our friends or family will have further comment."
63-year-old Arnold and 55-year-old Maria met in 1977 when Tom Brokaw introduced them at a charity event. They were married in 1986.