Summary of Significant Accounting Policies (Self Insurance Retention Liability) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Self insurance Retention Liability [Line Items]
Self insurance retention liability	$ 10,000	$ 10,000	$ 3,000
Annual aggregate limit	10,000
Self insurance retention liability additional deductible			5,000
Liability insurance coverage in excess of SIR policy	10,000	10,000	10,000
Self insurance retention Workers' compensation	2,000	$ 2,000	1,000
Letters of credit outstanding, amount	54,900
Minimum
Self insurance Retention Liability [Line Items]
Per claim range for the annual aggregate limit	10,000
Self insurance retention liability additional deductible applicable range - with SIR additional deductible			5,000
Maximum
Self insurance Retention Liability [Line Items]
Per claim range for the annual aggregate limit	15,000
Self insurance retention liability additional deductible applicable range - with SIR additional deductible			$ 10,000
State of Nebraska [Member]
Self insurance Retention Liability [Line Items]
Workers' compensation insurance bonds	25,600
Workers compensation insurance carrier [Member]
Self insurance Retention Liability [Line Items]
Workers' compensation insurance bonds	13,400
Insurance carrier [Member]
Self insurance Retention Liability [Line Items]
Letters of credit outstanding, amount	$ 43,000