This raid on the Fed's surplus account is supposed to be for the Highway Bill that was included in the Budget. Given the GD Congress' record, I wouldn't be surprised if it used the $19B for purposes other than intended.
From Forbes: "Federal Reserve Banks earn income by providing priced services to bank customers, and more so by their pro rata share of income earned on government securities. After covering operating expenses, paying their contractual dividends to bank owners of Fed stock and adjusting their surplus account to predetermined norms, they turn their excess earnings over to the Treasury’s general fund. All taxpayers get the benefit and that benefit has grown with the size of the Fed’s portfolio during these last few years.
The surplus account that the House bill is tapping may be thought of as a buffer between the total of Fed assets and liabilities. If the value of Fed assets were to shrink (depending on whether they use mark-to-market) they could conceivably wipe out the capital account and fall below Fed liabilities. That is why a capital buffer is needed, much like capital is needed to protect the solvency of regular banks."