Singer Britney Spears thinks maybe marrying Kevin Federline was not such a good idea.

In her upcoming MTV documentary, "Britney: For The Record," Spears said that she "married for all the wrong reasons."

She said that instead of following her heart, she did it "for just, like, the idea of everything."

Spears and Federline had two sons together, Sean Preston, 3, and Jayden James, 2. The couple's divorce became official in July 2007 after nearly three years of marriage.

Federline won custody of the children earlier this year. He receives $20,000 per month in child support payments from Spears, according to settlement documents.

The couple settled the long custody battle in July.

The documentary debuts at the end of November, just days before the release of her new CD, "Circus."