Employee Benefit Plans - Summary of Components of Net Periodic Benefit Cost and Other Amounts Recognized in Other Comprehensive Income (Detail) - USD ($)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Pension Plan [Member]
Net periodic benefit cost
Interest cost	$ 28,282	$ 2,958,903
Expected return on plan assets		(3,562,150)
Recognized actuarial (gain) loss due to settlements	(801,622)	(636,121)
Net periodic benefit cost	(773,340)	(1,239,368)
Supplemental Employee Retirement Plan [Member]
Net periodic benefit cost
Interest cost	319,143	340,262
Net periodic benefit cost	$ 319,143	340,262
Postretirement Benefits [Member]
Net periodic benefit cost
Service cost		11,860
Interest cost		26,269
Recognized actuarial (gain) loss		(2,079)
Curtailment charge (credit)		(1,678,920)
Recognized actuarial (gain) loss due to settlements		(169,089)
Net periodic benefit cost		$ (1,811,959)

Amount of gain (loss), recognized immediately as component of net periodic benefit (cost) credit, for change in value of benefit obligation or plan assets from experience different from that assumed, change in actuarial assumption, or consequence of temporarily deviating from substantive plan. Includes, but is not limited to, amount in excess of ten percent of greater of fair value of plan assets or benefit obligation.

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Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit plan.

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- Definition

Amount of cost recognized for passage of time related to defined benefit plan.

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Amount of net periodic benefit cost (credit) for defined benefit plan.

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Amount of gain (loss) recognized in net periodic benefit (cost) credit from event reducing expected years of future service of present employees or eliminating accrual of defined benefits for some or all future services of present employees.

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Amount of gain (loss) recognized in net periodic benefit (cost) credit from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk related to obligation and assets used to effect settlement.

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- Definition

Amount of cost for actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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