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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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