Reason why Nicole Kidman filed for divorce from Keith Urban revealed

Aussie actress Nicole Kidman and New Zealand country singer Keith Urban have decided to part ways after nearly 20 years of marriage.

Kidman tied the knot with Urban back in 2006, and the pair share two children, Sunday Rose, 17, and Faith Margaret, 14.

The two met and began dating in 2005, before getting engaged and marrying in Sydney, Australia, the following year.

Their marriage was Urban's first and Kidman's second, as she'd previously been married to fellow actor Tom Cruise from 1990 to 2001, with whom she shares two adopted children: Bella, 32, and Connor, 30.

On Tuesday (30 September), the Babygirl star petitioned to end her marriage in a Nashville court.

The news may come as a surprise to some fans, but documents have since revealed the reason behind the split.

Nicole Kidman, 58, and Keith Urban, 57, have decided to call it quits after 19 years of marriage (Larry Busacca/Getty Images)

The Guardian reports that such papers state the former couple has undergone 'marital difficulties and irreconcilable differences' with the filings including a marriage dissolution and childcare plan agreed on by the couple and submitted for a judge’s approval.

"The mother and father will behave with each other and each child so as to provide a loving, stable, consistent and nurturing relationship with the child even though they are divorced," the permanent parenting plan outlines.

It adds: "They will not speak badly of each other or the members of the family of the other parent. They will encourage each child to continue to love the other parent and be comfortable in both families."

Additionally, the parenting plan stipulates that the Eyes Wide Shut star be the primary residential parent to Sunday Rose and Faith Margaret, having them for 306 days per year, while their father, Urban, has them for the remaining 59 days.

The daughters have lived in Nashville their whole life, and the documents do not indicate that will change.

Official documents state the former couple has undergone 'marital difficulties and irreconcilable differences' (Taylor Hill / Contributor / Getty Images)

The filing also states that, because each parent earns over $100,000 per month, neither will need childcare or spousal support.

According to the Guardian, the marriage dissolution plan maps out a 'roughly equal' division of joint assets, with Kidman and Urban keeping all the assets that are in their own name, including the copyrights and royalties for their artistic work.

The arrangements also reportedly suggest that the divorce had been in the works for well over a month, at least.

Grammy Award-winning singer Urban signed the parenting plan on 29 August, while Kidman signed it the following week on 6 September.

Under Tennessee law, the divorce will take at least 90 days to become final.

Tyla has contacted Urban's and Kidman's representatives for comment.