Financial Instruments and Risk Management - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Derivative [Line Items]
Interest rate derivative losses reclassified into earnings	$ 47	$ 58
Loss reclassified from AOCI into earnings, tax	27	21
Accumulated other comprehensive loss	1,016		$ 1,193
Interest Rate Swap [Member]
Derivative [Line Items]
Accumulated other comprehensive loss	1,100		$ 1,100
Interest Rate Swap [Member] | Cash Flow Hedging [Member]
Derivative [Line Items]
Interest rate derivative losses reclassified into earnings	47	58
Loss reclassified from AOCI into earnings, tax	$ 27	$ 21