Derivative Instruments and Hedging Activities - Effects of Derivative Instruments on Statement of Comprehensive Income and Income Statement (Details) - Interest Rate Swap - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosures
Amount of (gain)/loss recognized in OCI on derivative	$ 1,957	$ (3,044)
Interest Expense
Derivative Instruments and Hedging Activities Disclosures
Amount of (gain)/loss reclassified from accumulated OCI into income	$ (841)	$ (28)