RLI Corp. posted a 6.2 percent increase in net earnings for 2012's third quarter compared to the same period a year ago despite reporting lower underwriting income and a reduced benefit from favorable prior-year reserves.

The Peoria, Ill. based specialty insurer says net earnings in the quarter were $25.5 million, up from $24 million in 2011's third quarter. While net investment income declined by 10.9 percent, the company saw $5.5 million in net realized investment gains for the period, compared to net realized losses of $177,000 a year ago. That, combined with a 2.3 increase in net-premiums earned, helped to push RLI's consolidated revenue up by 4.5 percent relative to 2011's third quarter.

While the company saw underwriting income for its casualty segment decline to $10.8 million in the quarter, compared to $22.2 million last year, RLI reduced underwriting losses in its property segment for the period to $300,000 from $1.8 million a year ago. Underwriting income for its surety segment was up to $8 million for the quarter compared to $1.1 million last year. The three segments together produced underwriting income of $18.5 million in 2012's third quarter, down from $21.5 million for the same period last year.