Pension and Other Postretirement Plans (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($) benefit_plan	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) benefit_plan	Sep. 30, 2019 USD ($)	Dec. 31, 2007
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Number of non-qualified defined benefit pension plans | benefit_plan	3		3
Number of healthcare plans | benefit_plan	2		2
Defined Benefit Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Vesting percentage in accrued benefits from plan freeze					100.00%
Service cost	$ 27,000	$ 24,000	$ 81,000	$ 72,000
Interest cost	168,000	210,000	505,000	630,000
Expected return on plan assets	(315,000)	(271,000)	(946,000)	(815,000)
Amortization of prior service cost	0	0	0	0
Amortization of net loss	145,000	165,000	435,000	495,000
Net periodic benefit cost	25,000	128,000	75,000	382,000
Minimum required contribution	0.0		0.0
Planned contributions remaining	0		0
Company contributions to plan			200,000
Chairman and President Non-Qualified Defined Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	302,000	126,000	907,000	377,000
Interest cost	337,000	256,000	1,012,000	768,000
Amortization of prior service cost	14,000	14,000	44,000	44,000
Amortization of net loss	1,446,000	348,000	4,336,000	1,044,000
Net periodic benefit cost	2,099,000	744,000	6,299,000	2,233,000
Company contributions to plan			1,600,000
Company expected contributions to plans in fiscal year	2,000,000.0		2,000,000.0
Defined Benefit Postretirement Healthcare Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Interest cost	41,000	49,000	124,000	148,000
Amortization of prior service cost	0	13,000	0	39,000
Amortization of net loss	40,000	61,000	119,000	183,000
Net periodic benefit cost	$ 81,000	$ 123,000	$ 243,000	$ 370,000
Minimum | Chairman and President Non-Qualified Defined Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Aggregate average annual participant salary increase			10.00%