For the first time since its iconic red headquarters opened 44 years ago, CNA Financial is paying rent on it.

The namesake tenant in “Big Red,” CNA's 44-story tower at 333 S. Wabash Ave., sold the building yesterday to Chicago development firm John Buck for $108 million, CNA spokeswoman Sarah Pang said.

Buck is building CNA a new, John Ronan-designed headquarters at 151 N. Franklin St. in the Loop, which will be called CNA Center.

Yesterday's sale of the 1.1 million-square-foot building is part of a unique deal in which the insurer signed a short-term lease to remain a tenant in the Wabash Avenue tower and a long-term deal for about 275,000 square feet in Buck's new tower in 2018.