Derivative Instruments and Hedging Activities (Narrative) (Details) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2021 USD ($) derivative_settled	Dec. 31, 2020 USD ($) derivative_settled
Derivative [Line Items]
Interest rate swap agreements settled | derivative_settled		0	0
Derivative liability fair value gross	$ 35,367	$ 35,367	$ 51,920
Interest Rate Swap
Derivative [Line Items]
Reduction in interest expense	700	2,200
Interest Rate Swap | Designated as Hedging Instrument
Derivative [Line Items]
Loss on derivative expected amount to be reclassified	17,300	17,300
Credit Risk Contract
Derivative [Line Items]
Derivative liability fair value gross	$ 37,400	$ 37,400	$ 54,600