Employee Benefit Plans - Fair value non-vested restricted shares (Details) - Retirement Income Plan - USD ($)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation exceeds fair value of the plan assets	$ (8,377,000)	$ (5,053,000)
Employer contribution	0	5,000,000
Accumulated other comprehensive loss, before tax	$ 3,043,000	$ 1,888,000	$ (1,650,000)
Expected long-term return assumption	7.00%	7.00%	7.00%

Amount, before tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan.

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Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Amount of funded (unfunded) status of defined benefit plan, measured as difference between fair value of plan assets and benefit obligation. Includes, but is not limited to, overfunded (underfunded) status.

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