Long-Term Debt (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Line of Credit Facility [Line Items]
Long-term debt	$ 0.0	$ 0.0
Restricted cash and investments	1.0	$ 1.1
BB&T Bank [Member]
Line of Credit Facility [Line Items]
Outstanding letter of credit balance	0.9
BB&T Bank [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Principal amount of the line of credit	$ 7.5
Line of Credit Facility, Affiliated Borrower	3
BB&T Bank [Member] | Revolving Credit Facility [Member] | Wall Street Journal Prime Rate [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	4.50%
Citizen's Bank [Member]
Line of Credit Facility [Line Items]
Outstanding letter of credit balance	$ 0.8
Citizen's Bank [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Principal amount of the line of credit	$ 5.0
Line of Credit Facility, Affiliated Borrower	3
Amount available at the reporting date	$ 4.0
Line of Credit Facility, Expiration Period	3 years
Percentage of letter of credit fees per annum	1.25%
Citizen's Bank [Member] | Revolving Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	2.25%