Derivative Instruments and Hedging Activities (Impact of Financial Instruments on Statement of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Effect of the Company's derivative financial instruments on the income statement
Total Interest Expense Presented in the Results of Operations in which the Effects of Cash Flow Hedges are Recorded	$ 31,439	$ 32,397	$ 65,649	$ 66,845
Interest Expense
Effect of the Company's derivative financial instruments on the income statement
Amount of Gain (Loss) Reclassified from AOCI into Operations	(3,041)	(3,359)	(6,014)	(4,509)
Interest Rate Swap
Effect of the Company's derivative financial instruments on the income statement
Amount of Gain (Loss) Recognized in AOCI on Derivatives	(1,136)	$ (4,197)	2,247	$ (36,248)
Amount of Gain (Loss) Reclassified from AOCI into Operations	$ 800		$ 1,500