Derivative Instruments and Hedging Activities - Effects of Derivative Instruments on Statement of Comprehensive Income and Income Statement (Details) - Interest Rate Swap - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative
Amount of (gain)/loss recognized in OCI on derivative for the year ended December 31,	$ 1,561	$ 1,847	$ (1,613)
Cash Flow Hedging | Interest Expense
Derivative
Amount of (gain)/loss reclassified from accumulated OCI into income for the year ended December 31,	$ 1,941	$ (832)	$ (256)