So yeah their balance sheet calculation did not show it as marked to market, but even accounting for that, they were still solvent at the end of 2022 according to their annual report: https://d18rn0p25nwr6d.cloudfront.net/CIK-0000719739/f36fc4d... page 95 (there were $15B of unrecognized losses mentioned, but even then they were solvent: $211,793M of assets -> $196,641M of assets assuming all Hold-to-maturity marked down to market, which is still more than the $195,498 of liabilities they had.
i see the total assets and liabilities numbers you mention on p. 95 of the 10-k you linked, but i don't see 15 billion dollars of unrealized losses anywhere, though i do see (for example on p. 124) 15724 million dollars of afs securities that had unrealized losses on them; but the unrealized losses themselves were only 1109 million dollars
i don't see anything in either report about unrealized losses on htm (non-afs) securities. in the 10-k (again p. 95) their htm securities are 91321 million dollars, almost 4× the size of their afs securities, and maybe they had about 20 billion dollars of loss of market value on those htm securities?
Re $15b: the line on the balance sheet about HtM notes that they're counting it as $91,321M for purposes of the balance sheet, but in a paranthetical note that it has $76,169M of fair market value (which is a difference of $15,152M).
But yeah that loss almost certainly continued going up in early 2023 as rates kept climbing.
