Cash Flows (Summary of Non-Cash Activities and Other Supplemental Data) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Non-Cash Investing and Financing Activities:
Treasury stock not yet settled	$ 0	$ 10,988
Finance lease additions	0	14,271
Capital expenditures incurred but not yet paid	2,314	2,501
Supplemental Data:
Cash interest paid	39,614	27,873
Income taxes paid, net	$ 2,314	$ 4,069