Financial Instruments (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Deferred compensation assets	[1]	$ 47,009	$ 42,161
Deferred compensation plan, assets		47,009	42,296
Deferred compensation liability		34,081	33,287
Deferred compensation plan, liability		35,135	33,357
Fair Value, Inputs, Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Deferred compensation assets	[1]	47,009	42,161
Deferred compensation plan, assets		47,009	42,296
Deferred compensation liability		34,081	33,287
Deferred compensation plan, liability		35,135	33,357
Interest Rate Swap No. 1 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Fair value of interest rate derivatives		$ 1,054	$ 70
Derivative, term of contract		10 years	10 years
Fair value of interest rate derivatives		$ (1,054)	$ (70)
Interest Rate Swap No. 1 [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Fair value of interest rate derivatives		$ 1,054	$ 70
Derivative, term of contract		10 years	10 years
Interest Rate Swap No. 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative, term of contract		5 years	5 years
Fair value of interest rate derivatives			$ 135
Interest Rate Swap No. 2 [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative, term of contract			5 years
Fair value of interest rate derivatives			$ 135

[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 arrangements.