Do I have to file Illinois State Income Tax while permanently living overseas as a federal employee?

I am a DOD civilian employee (federal civil service) living (in a German village) and working on a US military base in Germany. We sold our home and own no property in the US. I am still paying Illinois state income tax despite moving out of state in February 2016. Am I obligated to pay Illinois state income tax past February 2016? If not, how do I navigate this properly?