July 20 (Reuters) - Commercial insurer W. R. Berkley WRB.N reported a rise in second-quarter profit on Monday, boosted by robust investment gains and steady underwriting performance.

Demand for insurance remained resilient as households and businesses continued to seek protection against large and unpredictable losses.

Here are some details:

• The Greenwich, Connecticut-based insurer's net written premiums, a measure of policies written during the period, rose 2.4% to $3.43 billion in the quarter ended June 30.

  
  

• The company reported a combined ratio of 90% for the quarter, down from 91.6% ​in the year-ago period. A ratio below 100% shows that an insurer earned more in premiums than it paid out ​in claims.

  
  

• Net investment income rose 10.4% to $418.7 million in the second quarter.

  
  

• W. R. Berkley reported a quarterly profit for common stockholders amounting to $452.3 million, or $1.15 per share, up from $401.3 million, or $1 per share, last year.