Credit Performance/Credit Quality The following table provides a break-down by our internal credit ratings of our financial guaranty net par outstanding as  of December 31, 2012 and 2011, respectively: Net Par Outstanding (1) Rated  AAA  Net Par Outstanding (1)  Rated Non-AAA Investment  Grade  Net Par Outstanding (1)  Rated BIG Year Ended December 31, Year Ended December 31, Year Ended December 31, (in billions) 2012 2011 2012 2011 2012 2011 Type of Obligation Public Finance: General obligation and other tax supported . . . . . . . . . . . . . . $ — $ 0.1 $ 5.5 $ 15.1 $ 0.8 $ 0.6 Healthcare and long-term care . 0.3 0.4 2.7 4.7 0.2 0.3 Water/sewer electric/gas and investor-owned utilities . . . . . . 0.1 0.1 1.5 3.3 0.2 0.2 Education . . . . . . . . . . . . . . . . . — — 1.2 2.2 — — Airports/transportation . . . . . . . 0.1 0.1 0.7 2.9 0.3 0.3 Escrowed transactions (2) . . . . 1.0 1.4 — — — — Housing . . . . . . . . . . . . . . . . . . — — 0.1 0.3 — — Other Public Finance (3) . . . . . 0.1 0.1 0.5 0.8 — — Total Public Finance . . . . . 1.6 2.2 12.2 29.3 1.5 1.4 Structured Finance: CDO . . . . . . . . . . . . . . . . . . . . . 13.5 28.7 3.2 4.3 0.8 2.1 Asset-backed obligations . . . . . 0.1 0.2 0.2 0.3 0.5 0.4 Other structured (4) . . . . . . . . . — — 0.1 0.3 — — Total Structured Finance . . 13.6 28.9 3.5 4.9 1.3 2.5 Total . . . . . . . . . . . . . . . . . . . . . . . $ 15.2 $ 31.1 $ 15.7 $ 34.2 $ 2.8 $ 3.9 (1)  Represents our exposure to the aggregate outstanding principal on insured obligations. (2)  Escrowed transactions are legally defeased bond issuances where our financial guaranty policy is not legally extinguished  although cash or securities in an amount suf ficient to pay remaining obligations under such bonds have been deposited in  an escrow account for the benefit of the bond holders.  Although we have little to no remaining credit risk on these  transactions, they remain outstanding for GAAP  purposes.  (3)  Represents other types of municipal obligations, including human service providers, second-to-pay international public  finance, non-profit institutions, project finance accommodations and stadiums, none of which individually constitutes a  material amount of our financial guaranty net par outstanding.  (4)  Represents other types of structured finance obligations, including DPRs, collateralized guaranteed investment contracts  or letters of credit, foreign commercial assets and life insurance securitizations, none of which individually constitutes a  material amount of our financial guaranty net par outstanding. Notwithstanding the decrease in our financial guaranty net par outstanding in 2012, the ratings distribution of our insured  portfolio did not change significantly . In 2012, we experienced only a slight shift from non-AAA  investment grade obligations  to BIG obligations, which was almost entirely related to our public finance credits.  122