Pension and Other Postretirement Plans - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) benefit_plan	Dec. 31, 2019 USD ($)	Dec. 31, 2018	Dec. 31, 2007
Defined Benefit Plan Disclosure [Line Items]
Average rate of return	9.54%
Number of non-qualified defined benefit pension plan | benefit_plan	3
Number of healthcare plans | benefit_plan	2
Defined Benefit Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Vesting percentage in accrued benefits from plan freeze (in percentage)				100.00%
Actuarial gain (loss)	$ (2,153)	$ (1,398)
Discount rate	2.25%	3.00%	4.00%
Accumulated benefit obligation	$ 23,900	$ 22,700
Defined Benefit Pension Plans | Census Demographics
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	(587)	157
Defined Benefit Pension Plans | Change in Mortality
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	317	610
Defined Benefit Pension Plans | Difference in Expected and Actual Benefit Payments
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	(45)	16
Defined Benefit Pension Plans | Discount rate
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	(1,838)	(2,181)
Chairman and President Non-Qualified Defined Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	$ (21,736)	$ (7,438)
Discount rate	2.25%	3.00%	4.00%
Accumulated benefit obligation	$ 27,000	$ 19,800
Rate of compensation increase	8.00%	8.00%	8.00%
Chairman and President Non-Qualified Defined Benefit Plans | Minimum
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	10.00%
Chairman and President Non-Qualified Defined Benefit Plans | Change in Mortality
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	$ 441	$ 295
Chairman and President Non-Qualified Defined Benefit Plans | Discount rate
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	(5,457)	(3,401)
Chairman and President Non-Qualified Defined Benefit Plans | Increases in Actual Compensation More Than Actuarial Assumption
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	(16,720)	(4,332)
Defined Benefit Postretirement Healthcare Plans
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	$ (522)	$ (1,354)
Discount rate	2.25%	3.00%	4.00%
Accumulated benefit obligation	$ 6,500	$ 5,800
Defined Benefit Postretirement Healthcare Plans | Change in Mortality
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	656	283
Defined Benefit Postretirement Healthcare Plans | Difference in Expected and Actual Benefit Payments
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	104	121
Defined Benefit Postretirement Healthcare Plans | Discount rate
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	(893)	(974)
Defined Benefit Postretirement Healthcare Plans | Claims/Healthcare Cost Trend Experience
Defined Benefit Plan Disclosure [Line Items]
Actuarial gain (loss)	$ (389)	$ (784)