EXCLUSIVE: Nicole Kidman 'Desperate to Keep Peace' With Keith Urban As She's 'Terrified He'll Devastate Her Movie Fortune in Divorce'

Nicole Kidman is walking on eggshells around estranged husband Keith Urban, desperate to keep the peace as she faces fears that a messy divorce could jeopardize the fortune she's earned over decades in Hollywood, sources tell RadarOnline.com.

The Moulin Rouge! actress, 58, filed for divorce from the country star, 57, this month after 19 years of marriage.

Court documents filed in Nashville on Tuesday, September 30, revealed the pair had quietly signed a parenting plan weeks earlier, agreeing not to disparage each other around their daughters, Sunday, 17, and Faith, 14.

The documents also confirm Kidman will be the girls' primary residential parent, with Urban having them for 59 days a year. Both are required to attend a parenting seminar within 60 days of the filing.

Despite the calm tone of the legal paperwork, insiders suggest tensions are far from settled. A source close to the couple said: "Nicole is doing everything she can to avoid confrontation. She's terrified that if this turns ugly, Keith could come after her financially – and that could devastate everything she's built."

According to another insider, the Oscar-winning actress, whose estimated fortune exceeds $300 million, has grown increasingly anxious about protecting her assets.

"She’s proud of what she’s achieved – from The Hours to Big Little Lies – and she's worked for every cent," the source said. "Even with a pre-nup in place, she worries he might challenge parts of it. That's why she's so desperate to keep things civil."

Court filings show both parties waived any claim to spousal or child support, with Urban having already prepaid "child support obligations."

The agreement allows each to retain their own assets – a sign, lawyers say, of a strong prenuptial deal. Still, the suddenness of Kidman's filing took those close to her by surprise.

While she signed the paperwork on September 6, Urban had done so more than a week earlier, on August 29. Sources claim she made the decision to proceed "abruptly," after a summer spent apart.

Kidman had been filming Practical Magic 2 in London, while Urban was touring the US and Australia on his High and Alive world tour.

The distance, coupled with conflicting schedules, reportedly deepened the rift between them.

"Nicole never wanted things to end like this," a friend said. "She tried hard to hold the marriage together, but eventually she had to accept that they'd drifted beyond repair."

Kidman and Urban, who wed in Sydney in 2006, were once considered one of Hollywood's most enduring power pairs. They met shortly after Kidman's high-profile divorce from Tom Cruise, and their whirlwind romance quickly turned into marriage.

Together they built a home between Nashville and Sydney, often appearing on red carpets hand-in-hand, publicly declaring their love.