Revolving Credit Facility and Notes Payable (Narrative) (Details) - USD ($)			3 Months Ended	12 Months Ended
	Nov. 01, 2016	Dec. 17, 2015	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity			$ 15,000,000	$ 15,000,000
Line of credit facility, unused capacity, commitment fee percentage				0.25%
Line of credit facility, amount outstanding			0	$ 0
Facility B Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity			30,000,000	$ 30,000,000
Line of credit facility, commitment fee percentage				0.25%
Line of credit facility, commitment fee amount	$ 30,000	$ 75,000	30,000
Line of credit facility, amount outstanding			30,000,000	$ 30,000,000	$ 30,000,000
Line of credit facility, expiration date				Dec. 17, 2019
Letters of Credit [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity			$ 5,000,000	$ 5,000,000
Line of credit facility, commitment fee percentage				1.00%
London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate				2.50%
London Interbank Offered Rate (LIBOR) [Member] | Facility B Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate				3.00%