Reinsurer Swiss Re (SSREY) easily beat earnings expectations in the third quarter as it pushed the button on a Sfr1 billion ($1 billion) share buyback program.

The Zurich company, which is led by Christian Mumenthaler, said Thursday the group will start buying the stock on Friday. He attributed a smaller-than-expected decline in earnings to underwriting "discipline" and investment income, which is a source of much of insurers' profit.

Swiss Re said net profit fell to just under $1.2 billion from about $1.4 billion a year earlier. The figure was well above the $867 million forecast by analysts polled by FactSet. Premium income rose to Sfr8.6 billion from Sfr7.85 billion, above the Sfr8.1 billion predicted. But Swiss Re's return on equity slid to 12.8% from 17.3% as profit margins fell in all divisions apart from its life capital unit.

Swiss Re's so-called combined ratio -- a measure of insurers' profitability -- rose to 88.9% from 79.7%, edging closer to the 100%-plus territory which signals a loss.

Earnings per share fell to $3.54 from $4.09, above the EPS of about $2.36 predicted.

Swiss Re's shares were down 2.1% at Sfr90 in Zurich as of Wednesday close. The stock has held steady in the past year, as have shares in rival Munich Re.