Income Tax - (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Federal statutory income tax rate	34.00%
Unused business income tax credits	$ 2.1
AMT credit carryover	$ 1.4
ATM credit carryforward, expiration period	unlimited
Unused business income tax expiration year	Dec. 31, 2029
State net operating loss	$ 17.9
State net operating loss expiration year	Dec. 31, 2023
Recognized deferred income tax liability	$ 14.7
Unrecorded deferred income tax liability	3.1
Effect of "Tax Cuts and Jobs Act"	$ 2.0
Scenario, Plan [Member]
Federal statutory income tax rate	21.00%