Americans who refuse to buy affordable medical coverage could be hit with fines of more than $1,000 under a health care overhaul bill unveiled Thursday by key Senate Democrats looking to fulfill President Barack Obama's top domestic priority. The Congressional Budget Office estimated the fines will raise around $36 billion over 10 years. Senate aides said the penalties would be modeled on the approach taken by Massachusetts, which now imposes a fine of about $1,000 a year on individuals who refuse to get coverage. Under the federal legislation, families would pay higher penalties than individuals. In a revamped health care system envisioned by lawmakers, people would be required to carry health insurance just like motorists must get auto coverage now. The government would provide subsidies for the poor and many middle-class families, but those who still refuse to sign up would face penalties. Called shared responsibility payments," the fines would be set at least half the cost of basic medical coverage, according to the legislation. The goal is to nudge people to sign up for coverage when they are healthy, not wait until they get sick. The legislation would exempt certain hardship cases from fines. The fines would be collected through the income tax system. Obama wants a bill this year that would provide coverage to the nearly 50 million Americans who lack it and reduce medical costs. In a statement, Obama welcomed the legislation, saying it "reflects many of the principles I've laid out." The government's costs would be covered by a combination of higher taxes and cuts in projected Medicare and Medicaid spending.