Revolving Credit Facility and Notes Payable (Narrative) (Details)	12 Months Ended
	Dec. 31, 2018 USD ($)
Facility A Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 15,000,000
Line of credit facility, unused capacity, commitment fee percentage	0.25%
Line of credit facility, amount outstanding	$ 0
Facility A Revolving Credit Sub-Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 5,000,000
Line of credit facility, unused capacity, commitment fee percentage	1.00%
Facility B Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 30,000,000
Line of credit facility, unused capacity, commitment fee percentage	0.25%
Line of credit facility, amount outstanding	$ 30,000,000
London Interbank Offered Rate (LIBOR) [Member] | Facility A Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Interest Rate During Period	2.50%
London Interbank Offered Rate (LIBOR) [Member] | Facility B Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, unused capacity, commitment fee percentage	3.00%