CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
CONSOLIDATED BALANCE SHEETS
Allowance for doubtful accounts	$ 6,765	$ 4,815
Accumulated depreciation	$ 763,304	$ 790,712
Preferred stock, par value (in dollars per share)	$ 0.10	$ 0.10
Preferred stock, shares authorized (in shares)	1,000,000	1,000,000
Preferred stock, shares issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.10	$ 0.10
Common stock, shares authorized (in shares)	349,000,000	349,000,000
Common stock, shares issued (in shares)	215,628,716	214,951,093
Common stock, shares outstanding (in shares)	215,628,716	214,951,093