Equity Plan - Unrecognized Compensation Cost - Nonvested Restricted Stock Awards (Details) - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Unrecognized Compensation Cost
Total compensation cost	$ 1,924,000	$ 1,817,000	$ 1,750,000
Total income tax benefit on share-based compensation cost	239,000	$ 424,000	$ 146,000
Restricted stock
Unrecognized Compensation Cost
Total unrecognized compensation cost related to nonvested restricted stock awards	$ 2,340,000
Expected weighted-average period for recognition of compensation costs related to nonvested restricted stock awards	2 years 1 month 10 days

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

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Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

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