Significant Accounting Policies (Stock-based Compensation and Other) (Details) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Schedule of Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount of directors, annual retainer paid in restricted shares	$ 95,000
Annual non-employee directors retainer amount	155,000
Chairman
Schedule of Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amount of directors, annual retainer paid in restricted shares	150,000
Annual non-employee directors retainer amount	$ 250,000
Class A Common Stock \| Executives \| Share-based Payment Arrangement [Member]
Schedule of Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued during the year under the Company's stock compensation plans (shares)	85,567	96,153
Class A common stock available for issuance under the plan (shares)	414,433
Compensation expense related to share awards	$ 4,100,000	$ 3,400,000
Compensation expense related to share awards, net of tax	$ 3,300,000	2,700,000
Class A Common Stock \| Non-employee directors \| Share-based Payment Arrangement [Member]
Schedule of Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Class A common stock available for issuance under the plan (shares)	77,310
Compensation expense related to share awards	$ 1,100,000	900,000
Compensation expense related to share awards, net of tax	$ 900,000	$ 700,000
Class A Common Stock \| Non-employee directors \| Restricted stock
Schedule of Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued during the year under the Company's stock compensation plans (shares)	22,258	26,968
Amount of directors, annual retainer paid in restricted shares		$ 90,000
Annual non-employee directors retainer amount		$ 150,000
Percentage of annual retainer that may be received in shares of Class A stock (percent)	100.00%
Class A Common Stock \| Non-employee directors \| Voluntary shares
Schedule of Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued during the year under the Company's stock compensation plans (shares)	432	560
Class A Common Stock \| Participant's retirement date \| Executives \| Share-based Payment Arrangement [Member]
Schedule of Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Duration of restrictions on stock assignment, pledges or transfers	3 years
Class A Common Stock \| Participants retirement from board of directors \| Non-employee directors \| Share-based Payment Arrangement [Member]
Schedule of Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Duration of restrictions on stock assignment, pledges or transfers	5 years
Class A Common Stock \| Minimum age of director upon retirement from board \| Non-employee directors \| Share-based Payment Arrangement [Member]
Schedule of Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Duration of restrictions on stock assignment, pledges or transfers	70 years
Class A Common Stock \| Award date \| Executives \| Share-based Payment Arrangement [Member]
Schedule of Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Duration of restrictions on stock assignment, pledges or transfers	5 years
Class A Common Stock \| Award date \| Non-employee directors \| Share-based Payment Arrangement [Member]
Schedule of Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Duration of restrictions on stock assignment, pledges or transfers	10 years
Minimum \| Class A Common Stock \| Award date \| Executives \| Share-based Payment Arrangement [Member]
Schedule of Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Duration of restrictions on stock assignment, pledges or transfers	3 years
Maximum \| Class A Common Stock \| Award date \| Executives \| Share-based Payment Arrangement [Member]
Schedule of Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Duration of restrictions on stock assignment, pledges or transfers	10 years

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