Credit Facilities (Narrative) (Details) - Revolving Credit Facility	Jul. 27, 2017	Jan. 31, 2019 USD ($) letter_of_credit	Dec. 31, 2018 USD ($) letter_of_credit
Line of Credit Facility [Line Items]
Liquidity requirement, minimum			$ 25,000,000
Long-term line of credit			0
Subsequent Event
Line of Credit Facility [Line Items]
Long-term line of credit		$ 0
Ninth Amendment | London Interbank Offered Rate (LIBOR)
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.75%
Tenth Amendment
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity			15,000,000.00
LIBOR Rate Loan
Line of Credit Facility [Line Items]
Standby letters of credit, total amount outstanding			$ 500,000
Number of standby letters of credit outstanding | letter_of_credit			1
Remaining borrowing capacity			$ 5,500,000
LIBOR Rate Loan | Subsequent Event
Line of Credit Facility [Line Items]
Standby letters of credit, total amount outstanding		$ 500,000
Number of standby letters of credit outstanding | letter_of_credit		1