Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Allowance for doubtful accounts receivable	$ 6,845	$ 7,035
Accumulated Amortization	$ 267,115	$ 235,582
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, authorized shares (in shares)	800,000,000	800,000,000
Common stock, issued shares (in shares)	324,418,632	324,418,632
Treasury stock, shares (in shares)	103,438,458	104,918,360