Fair Value Measurements (Schedule of Assets and Liabilities Measured at a Fair Value on Recurring Basis) (Details) - Recurring Basis [Member] - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments related to deferred compensation liabilities	$ 924,000	$ 948,000
Deferred compensation liabilities	937,000	952,000
Interest rate swaps liability	13,208,000	18,927,000
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments related to deferred compensation liabilities	924,000	948,000
Deferred compensation liabilities	937,000	952,000
Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps liability	$ 13,208,000	$ 18,927,000