Pension And Other Liabilities (Narrative) (Details) - USD ($)				12 Months Ended
		Mar. 12, 2020	Aug. 28, 2019	Dec. 31, 2020	Dec. 31, 2019	Mar. 29, 2021	Jun. 30, 2020	Jan. 01, 2019	Aug. 29, 2014
Defined Benefit Plan Disclosure [Line Items]
Total operating property				$ 353,125,000	$ 258,138,000			$ 258,037,000
Operating lease liabilities - current				22,699,000	20,379,000			$ 245,280,000
Accrued pension liability				4,048,000	4,469,000				$ 7,500,000
Benefit obligation, gross				$ 10,200,000
Discount rate				4.25%
Discount term				15 years
Monthly estate payment amount				$ 57,000
Discounted value				2,700,000
Accumulated prior service cost				$ 3,100,000
Accumulated prior service cost amortization period				15 years
Accrued pension costs included in other liabilities				$ 4,700,000	5,200,000
Service cost				0	0
Lease liability	[1]			$ 5,900,000	$ 5,900,000
Sutton Hill Capital, LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Lease expiration date				Jun. 30, 2020
Chief Executive Officer [Member]
Defined Benefit Plan Disclosure [Line Items]
Estimated amortization of prior service cost next fiscal year				$ 207,000
Supplemental Executive Retirement Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Accrued pension liability									$ 7,600,000
Village East Cinema [Member]
Defined Benefit Plan Disclosure [Line Items]
Lease expiration date		Jan. 31, 2022
Operating lease liabilities - current				$ 0.0
Lease term				13 years
Payment to acquire property			$ 5,900,000
Village East Cinema [Member] | Sutton Hill Capital, LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Purchase option				$ 5,900,000			$ 5,900,000
Total operating property				4,700,000
Operating lease liabilities - current				$ 5,900,000
Lease term				10 years
Subsequent Event [Member] | Village East Cinema [Member] | Sutton Hill Capital, LLC [Member]
Defined Benefit Plan Disclosure [Line Items]
Purchase option						$ 5,900,000

[1] Represents the lease liability of the option associated with the ground lease purchase of the Village East Cinema. See below for more information.