Senate lawmakers released their first draft of a bipartisan bill Sunday spelling out their proposal, previously announced last week, to eliminate Fannie Mae and Freddie Mac. The legislation replaces the mortgage-finance giants with a new system in which the government would continue to play a potentially significant role insuring U.S. home loans.

The 442-page bill, introduced by the heads of the Senate Banking Committee, Sens. Tim Johnson (D., S.D.) and Mike Crapo (R., Idaho), would construct an elaborate new platform by which a number of private sector entities, together with a government-administered utility, would replace key roles long played by Fannie and Freddie.

Fannie and Freddie don’t make loans, but instead buy them from lenders, package them into securities, and sell those bonds to investors. They guarantee to make investors whole if loans default, attracting a diverse range of investors to the U.S. mortgage market.

Over the past three decades, the companies facilitated the development of broad and deep markets for mortgage bonds, which helped make more widely available the 30-year, fixed-rate mortgage to American borrowers. The companies were taken over by the government in 2008 as they neared collapse.