Retirement and Benefit Plans (Details) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2020 USD ($) Integer7	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)
Net periodic benefit cost [Abstract]
Net periodic benefit expense			$ 1,492	$ 2,687
Pension contributions [Abstract]
Pension contributions			12,659	1,324
Number of Repurchased Real Property \| Integer7	2
Pension Plan [Member]
Net periodic benefit cost [Abstract]
Service cost	$ 167	$ 163	501	485
Interest cost	1,474	1,792	4,420	5,417
Expected return on plan assets	(1,374)	(1,477)	(4,120)	(4,426)
Amortization of actuarial (gain) loss	202	(44)	605	(131)
Plan settlement loss	0	1,342	86	1,342
Net periodic benefit expense	469	$ 1,776	1,492	$ 2,687
Pension contributions [Abstract]
Pension contributions			12,700
Estimated remaining 2020 pension contributions	100		$ 100
Pension Plan Repurchases [Member]
Pension contributions [Abstract]
Pension contributions	$ 11,400

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Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit plan.

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Amount of contribution expected to be received by defined benefit plan from employer in remainder of current fiscal year. Excludes contribution previously paid by employer in current fiscal year.

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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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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 irrevocable action relieving primary responsibility for benefit obligation and eliminating risk related to obligation and assets used to effect settlement.

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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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Amount of cash outflow for pension benefit. Includes, but is not limited to, employer contribution to fund plan asset and payment to retiree. Excludes other postretirement benefit.

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