Thus far, 19 states have not expanded Medicaid eligibility under the Affordable Care Act (ACA). According to a Brief from the Urban Institute, broad fiscal reviews conducted in expansion states have found that federal offsets have exceeded state cost increases, so expansion has improved state budget balances. Most such reviews forecast that state budget gains from expansion will continue into the indefinite future.
The Brief can be accessed at http://www.urban.org/sites/default/files/alfresco/publication-pdfs/2000886-The-Cost-to-States-of-Not-Expanding-Medicaid.pdf.