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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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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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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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Stock Based Compensation (Details) - USD ($)	3 Months Ended		12 Months Ended
Stock Based Compensation (Details) - USD ($)	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Total charge to operations:
Total charge to operations	$ 976,000	$ 954,000
Restricted stock and RSU grants
Restricted stock and RSU grants:
Weighted average per share value of non-vested shares (based on grant price) (in dollars per share)	$ 25.52	$ 24.60
Value of stock vested during the year (based on grant price)	$ 3,004,000	$ 2,304,000
Restricted stock
Stock Based Compensation
Vesting period	5 years
Summary of the activity of the incentive plans
Average per share grant price (in dollars per share)	$ 28.10	$ 25.70
Deferred compensation to be recognized over vesting period	$ 4,202,000	$ 3,856,000
Number of non-vested shares:
Non-vested beginning of period (in shares)	674,250	651,250	651,250
Number of shares awarded	149,550	150,050
Vested during year (in shares)	(122,125)	(112,150)
Non-vested end of period (in shares)	701,675	689,150	674,250	651,250
Total charge to operations:
Total charge to operations	$ 875,000	$ 843,000
Total compensation costs related to non-vested awards that have not yet been recognized	$ 10,468,000
Weighted average remaining vesting period	2 years 10 months 24 days
RSUs
Stock Based Compensation
Number of shares forfeited	0		5,250
Number of non-vested shares:
Non-vested beginning of period (in shares)	225,026	152,500	152,500
Number of shares awarded			77,776	76,250	76,250
Vested during year (in shares)	0
Forfeitures (in shares)	0		(5,250)
Non-vested end of period (in shares)	225,026	152,500	225,026	152,500
Total charge to operations:
Total charge to operations	$ 101,000	$ 111,000
Total compensation costs related to non-vested awards that have not yet been recognized	$ 907,000
Weighted average remaining vesting period	1 year 2 months 12 days
TSR Awards
Stock Based Compensation
Percentage of RSUs to vest upon achievement of specified criteria	50.00%
ROC Awards
Stock Based Compensation
Percentage of RSUs to vest upon achievement of specified criteria	50.00%
2019 Incentive Plan
Stock Based Compensation
Maximum number of shares authorized for issuance	750,000
Number of non-vested shares:
Number of shares awarded	224,576
2019 Incentive Plan \| Restricted stock
Number of non-vested shares:
Number of shares awarded	149,550
2019 Incentive Plan \| RSUs
Number of non-vested shares:
Number of shares awarded	75,026
2016 and 2012 Incentive Plans
Number of non-vested shares:
Non-vested end of period (in shares)	702,125
2016 and 2012 Incentive Plans \| Restricted stock
Number of non-vested shares:
Non-vested end of period (in shares)	552,125
2016 and 2012 Incentive Plans \| RSUs
Number of non-vested shares:
Non-vested end of period (in shares)	150,000
Pay-for-performance program \| RSUs \| Awards granted in 2017
Stock Based Compensation
Aggregate fair value of the shares granted	$ 807,000
Pay-for-performance program \| RSUs \| Awards granted in 2018
Stock Based Compensation
Aggregate fair value of the shares granted	690,000
Pay-for-performance program \| RSUs \| Awards granted in 2019
Stock Based Compensation
Aggregate fair value of the shares granted	$ 729,000