Workers' Compensation Expense (Schedule of Amounts Recognized in Balance Sheet) (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accrued Workers' Compensation [Line Items]
Total obligations	$ 238,307	$ 259,954
Less amount included in accrued expenses	14,202	15,259
Noncurrent obligations	224,105	244,695
Occupational disease
Accrued Workers' Compensation [Line Items]
Occupational disease costs	167,585	183,001	$ 158,325
Total workers' compensation expense
Accrued Workers' Compensation [Line Items]
Occupational disease costs	$ 70,722	$ 76,953