Keith Urban and Nicole Kidman are celebrating 12 years of marriage on Monday (June 25). While the couple have now been together well over a decade, Urban admits that he and Kidman, who he often lovingly refers to as "baby girl," are continuously working on their marriage.

"I'm a work in progress," he told several media outlets backstage at 2018 CMA Music Festival (quote via the Boot). "We're just like any married couple, trying to figure out what works and what doesn't work. Trying to balance work and family life is challenging for everyone, and it's no different for us."

Asked if there is a secret to their successful marriage, Urban explains that they both have an unwavering commitment to each other.

See Keith + Nicole's Sweetest Pictures Through the Years

"We're very, very 'in it' as a couple: very awake, very present and very in love," he says. "When it does go out of balance, we fix it quickly. We do whatever we've got to do. We travel, we do whatever it takes to not be apart."

When they have to be apart due to work obligations, each partner makes sure to keep in touch with the other while away. Urban was recently out of town headlining a festival on Kidman's birthday, so instead of simply calling his wife to wish her a happy birthday, he got a little help from his audience.

The "Coming Home" singer selfied a birthday serenade while onstage at Country USA Festival in Oshkosh, Wisc., last week, asking a few thousand fans up front to participate. The best part? They don't call Urban's wife by her name in the song, but instead refer to her as "baby girl."

Watch Keith Urban and Nicole Kidman Sing Together: 

See Keith Urban Adoring Nicole Kidman on the Red Carpet