Historic Tax Credits - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Historic Tax Credits [Abstract]
Historic Tax Credit put option received			$ 1.0
Amount paid in cash			0.9
Priority Return Expense	$ 0.2	$ 0.2	0.1
Tax Credit Amortization Income	$ 1.0	$ 1.9
Interest and Other Income			$ 0.8	$ 1.8