Bond insurer Assured Guaranty (AGO) posted a second-quarter profit of $376.5 million, or $2.01 a share, on a net fair value gain of $263.6 million.

That compares to a net loss of $43.1 million, or 23 cents a share, a year earlier when the firm reported $187.5 million in net fair value losses.

"Interest rates, which were already at historically low levels, declined further in second quarter 2012, which resulted in a net increase in expected losses, that does not represent additional credit impairment, but rather a change in the risk-free rates used to discount losses," Assured Guaranty wrote in its second-quarter earnings report.

The firm's CEO and president Dominic Frederico said the insurer's second quarter results reflect Assured Guaranty's versatility and strength.

"In U.S. public finance, we continued to honor our value proposition by providing protection to holders of insured bonds, including those of distressed municipalities such as Harrisburg, Jefferson County and Stockton," said Frederico.

Assured Guaranty and its affiliate companies insure everything from municipal bonds in the U.S., structured finance transactions -- which are in some cases tied to mortgage securities -- and international infrastructure financings.