Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 39,800	$ 36,622
Accumulated depreciation	$ 1,296,920	$ 1,268,170
Preferred stock, par value (usd per share)	$ 1	$ 1
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (usd per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	450,000,000	450,000,000
Common stock, shares issued (in shares)	144,458,057	144,354,335
Common stock, shares outstanding (in shares)	144,458,057	144,354,335