Compensation and Benefit Plans - Summary of Pension Plan Funded Status and Amounts Recognized in Financial Condition Statements (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Sep. 30, 2019	Dec. 31, 2018
Defined Benefit Pension Plans And Defined Benefit Postretirement Plans Disclosure [Abstract]
Projected benefit obligation	$ (14,175)	$ (15,883)	$ (14,244)	$ (14,175)	$ (14,244)
Fair value of plan assets	14,179	14,732	14,416	14,179	14,416
Funded status				4	172
Accumulated benefit obligation				$ (14,175)	$ (14,244)
Changes in benefit obligation:
Beginning of period	14,244	15,883	15,883
Service cost	29	30	39
Interest Cost	442	406	542
Interest rate change			(1,691)
Mortality change			(41)
Loss on accumulated benefit obligations	4		243
Administrative cost	(29)		(39)
Benefits paid	(515)		(692)
End of period	14,175		14,244
Changes in plan assets:
Fair value of plan assets, beginning of period	14,416	14,732	14,732
Actual return on plan assets	307		415
Benefits paid	(515)	$ (524)	(692)
Administrative expenses paid	(29)		(39)
Fair value of plan assets, end of period	$ 14,179		$ 14,416

Defined benefit plan administrative cost.

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- Definition

Defined benefit plan interest rate changes.

+ References

No definition available.

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- Definition

Defined benefit plan mortality changes.

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Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level.

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Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

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Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.

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Amount of administration expense of defined benefit plan which decreases plan assets. Excludes plan administration expense paid by employer.

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No definition available.

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

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Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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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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No definition available.

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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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- Definition

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

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

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Amount of payment to participant under defined benefit plan which decreases plan assets. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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

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