The parent company of Tacoma-based Columbia Bank on Thursday reported third-quarter profit of $11.9 million, or 30 cents a share, down from $18.9 million, or 48 cents a share, in the same period last year.

The company attributed the decline to 2011’s third-quarter profit getting a boost from its acquisition of a failed bank.

Bank officials said the company benefitted this quarter from a drop in nonperforming loans and higher income from merchant card services and bank fees.