Chubb Ltd. saw its net profit double to $2.42 billion in the fourth quarter of 2020, as it benefited from double-digit commercial lines premium growth amid a continuing hard or firming market in most parts of the world.

“We had a very strong finish to the year, excellent financial results, headlined by rapid premium revenue growth and margin improvement — a trend we are confident will continue,” said Evan G. Greenberg, chairman and CEO of Chubb, on a Wednesday morning earnings call with analysts.

“In the quarter, we continued to experience a strong and continuously improving commercial property/casualty pricing environment globally. In fact, the level of rate and rate of increase was the strongest since this part of the underwriting cycle began approximately three years ago,” Mr. Greenberg said.

While nearly all of Chubb’s commercial property/casualty lines are achieving rates that exceed loss costs, others have a way to go, he said.

“The rate environment, in my judgment, is a rational and necessary response to years of underpricing of risk and a more uncertain risk environment today,” Mr. Greenberg said.

Net premium written increased to $7.77 billion in the fourth quarter, up 5.4% over the same period in 2019, Chubb said.

Pretax catastrophe losses were $314 million for the quarter, or $271 million net, down 27% from the year-earlier period. There were no changes to the previously reported aggregate property/casualty COVID-19-incurred loss charge, Mr. Greenberg said.

Chubb’s property/casualty combined ratio was 87.6%, compared with 92.7% in the same period in 2019.

The current commercial market conditions have legs, and Chubb expects the favorable underwriting conditions to continue, Mr. Greenberg said.

Overall rates in North America commercial property/casualty increased by 16.5% in the quarter.

In major accounts primary casualty rates were up 7%, while general casualty rates were up over 36%.  Property rates were up over 30%, while financial lines rates were up over 26%.

In Chubb’s Westchester E&S wholesale business, property rates were up over 23%, casualty rates were up nearly 29%, and financial lines rates were up over 26%.

In Chubb’s middle-market business, rates for property were up over 15%. Casualty rates were up nearly 12%, excluding workers compensation (up 0.5%), and financial lines rates were up over 20%.

“Internationally, like in the U.S. in those markets where we grew, we continued to achieve improved rate to exposure across the commercial portfolio,” Mr. Greenberg said.

In its overseas general business, rates were up 18.5% overall, while rates were up 17% in international retail and 26% in London wholesale.

For the full year, Chubb’s profit fell by 20.7% to $3.53 billion, and net premium written increased to $31.31 billion, up 4.8% compared with 2019. Chubb’s 2020 combined ratio was 96.1%, compared with 90.6% the prior year.

“Looking forward, we have made a good start to the year in the first quarter — both the growth and level of rate increase we are achieving look a lot like the fourth quarter,” Mr. Greenberg said.