Financial Instruments (Details) - USD ($) $ in Thousands		6 Months Ended	12 Months Ended
		Jun. 30, 2020	Dec. 31, 2019
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets	[1]	$ 44,056	$ 47,009
Deferred compensation plan, assets		44,056	47,009
Deferred compensation liability		33,861	34,081
Deferred compensation plan, liability		37,482	35,135
Interest Rate Swap No. 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of interest rate derivatives		$ 2,446	$ 1,054
Derivative, term of contract		10 years	10 years
Interest Rate Swap No. 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of interest rate derivatives		$ 1,175
Derivative, term of contract		5 years
Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation assets	[1]	$ 44,056	$ 47,009
Deferred compensation plan, assets		44,056	47,009
Deferred compensation liability		33,861	34,081
Deferred compensation plan, liability		37,482	35,135
Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap No. 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of interest rate derivatives		$ 2,446	$ 1,054
Derivative, term of contract		10 years	10 years
Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap No. 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of interest rate derivatives		$ 1,175
Derivative, term of contract		5 years

[1] Deferred compensation assets consist of the cash surrender value of life insurance policies and are intended to assist in the funding of the deferred compensation agreements.