I still prefer 157, but 163 is a good one too...

From the FASB:

Statement 163 requires that an insurance enterprise recognize a claim liability prior to an event of default (insured event) when there is evidence that credit deterioration has occurred in an insured financial obligation.

Specifically, from the standard itself:

The recognition approach for a claim liability relating to a financial guarantee insurance contract requires that an insurance enterprise recognize a claim liability when the insurance enterprise expects, based on the present value of expected net cash outflows to be paid under the insurance contract discounted using a risk-free rate, that a claim loss will exceed the unearned premium revenue.

For the monolines, of course, that means a realistic assessment of eventual credit losses. Now that isn't an easy thing to do, and there is still a lot of wriggle room in how that standard is applied, but at least sticking their heads in the sand is no longer a sanctioned accounting standard.