Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets:
Trade accounts receivable, allowances for doubtful accounts	$ 289	$ 6,824
Equity:
Common stock, par value (in dollars per share)	$ 0.01
Common stock, shares authorized (in shares)	250,000,000
Common stock, shares issued (in shares)	130,075,838	128,304,354
Treasury stock, shares held (in shares)	3,138,675	2,953,976