NEW YORK (CNN/Money) - Everybody is so agog over how much money General Motors raised Thursday that there hasn't been too much discussion of exactly where the money is going: Right into the market.

GM's big debt offering looked big enough at the beginning of the week, when it was pegged at $13 billion. But heavy demand from investors desperate for any sort of yield pushed the offering up steadily. Estimates swelled to $15.5 billion, then to $16.5 billion and once was all said and done, the offering rang in at $17.6 billion.

The point of the offering was to help plug up GM's pension fund, which Credit Suisse First Boston's accounting group estimates is underfunded to the tune of $25.4 billion. As a result, the market extracted far less yield from GM than it might have if the offering was going toward something else -- the understanding is that the car company is merely shifting its liabilities from its pension fund onto its balance sheet, which means that it really isn't any more in the hole than it was already.

The odd thing is that GM has, in a sense, raised all this cash from investors only to give it right back. The money will flow into its pension fund and its pension fund managers will use it to buy stocks, bonds and other debt instruments.

"GM's going out to the markets to get the money and they're going to put it back into the market, so in a sense it's a wash," said Brian Reynolds, fixed-income strategist at Kirlin Securities.

But while it may be a zero-sum game looking across markets, it also represents a big reallocation of capital within markets. The typical pension fund operates on a 60/40 basis -- 60 percent stocks and 40 percent debt. GM's pension has been a little lighter on stocks, so perhaps half of the money it's raised -- $8 or $9 billion, say -- will be heading into stocks. That's a substantial amount of cash, and could help fuel the stock rally.

There is probably more coming. Ford, whose pension plan is, according to Credit Suisse First Boston, $15.6 billion underfunded seems like it could be a likely candidate, as could Exxon, which is underfunded by $11.3 billion. All told, according to Standard & Poor's, the pension plans of companies in the S&P 500 are underfunded by $225.9 billion dollars.

"There are a lot of traditional brick-and-mortar companies which have really underfunded pensions," said D.A. Davidson bond trader Mary Ann Hurley. "The word I'm hearing is we'll be seeing more of these deals."