Direct auto insurer Geico led the way, turning in an underwriting profit of $680 million in 2012. The profit would have been $410 million more if not for a change in accounting rules at the start of 2012, Buffett says.

“When I count my blessings, I count Geico twice,” says Buffett, who continues by pointing out the insurer's results were accomplished in the face of its largest single loss in history—Superstorm Sandy.

“We insured 46,906 vehicles that were destroyed or damaged in the storm,” says Buffett. Sandy cost Geico more than three times its previous record-setting loss—Hurricane Katrina in 2005.

Geico took losses of $490 million Sandy during 2012's fourth quarter and booked catastrophe losses of $638 million for the year.

Berkshire insurance operations recorded aggregate pre-tax losses of about $1.1 billion from Sandy.

Geico's premiums increased 9 percent to $16.7 billion year-over-year, from an increase in policy count, and an increase in premium per policy. Buffett says renewals and the percentage of quotes resulting in sales were each up.

“I rub my eyes when I look at what [Geico CEO Tony Nicely has accomplished],” Buffett says. “Much more growth lies ahead.”

At other insurance operations, Berkshire Hathaway Reinsurance Group, led by Ajit Jain, reversed a $714 million underwriting loss in 2011 to a profit of $304 million in 2012. And General Re more than doubled yearly underwriting profit to $355 million from $144 million in 2011.

Results at General Re included $266 million of catastrophe losses from Sandy, an earthquake in Northern Italy and tornadoes in the U.S. Midwest.