Keith Urban showers Nicole Kidman with love letters when they apart.

The 'Railway Man' star, who has daughters Sunday Rose, five, and Faith Margaret, three, with the 'Put You in a Song' singer, says he is extremely romantic, especially when their hectic work schedules force them to be away from each other.

The 46-year-old actress told the US March issue of InStyle magazine: ''For every single night he's away, he leaves me a love letter. Every single night of our relationship. It keeps us close.''

When Nicole isn't filming, she enjoys accompanying the 'American Idol' judge on tour with their daughters, because she gets to indulge on fast food.

She said: ''Keith and I eat at Wendy's. You've got to remember, I'm with a musician on a tour bus. We do drive-throughs!''

The 'Grace of Monaco' star also credits her children for helping her embrace a more relaxed approach to things, including her hair.

She explained: ''I almost never straighten it anymore. It's taken me 40-something years, but I embrace the curl. My littlest daughter has the same hair. She likes it when my hair is curly, so I wear it for her.''