Medicaid Expansion Parity Act of 2017 This bill amends title XIX (Medicaid) of the Social Security Act to provide the enhanced federal medical assistance percentage (FMAP) to every state that expands Medicaid coverage for individuals who are newly eligible under the Patient Protection and Affordable Care Act, regardless of when such expansion takes place. Under current law, the enhanced FMAP is equivalent to 100% in 2014 through 2016, 95% in 2017, 94% in 2018, 93% in 2019, and 90% thereafter. The bill retains this enhanced FMAP, but bases it on a term of years rather than on specific dates. The bill applies retroactively.