This excerpt taken from the PNC 10-Q filed May 11, 2009.
OTTIOther Debt Securities
During the first quarter of 2009, we recorded credit losses of $4 million on two other debt securities. To measure credit losses we compile relevant collateral details and performance statistics on a security-by-security basis. The securities are then assessed, considering the external credit rating, market price, security performance, and the creditworthiness of the counterparty.
Information relating to securities gains and losses is set forth in the following table.