Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Allowance for doubtful accounts, current	$ 61,879	$ 59,906
Accumulated amortization of other intangible assets	26,715	23,466
Allowance for doubtful accounts, noncurrent	$ 6,135	$ 7,895
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock authorized (in shares)	100,000,000	100,000,000
Common stock issued (in shares)	75,997,000	75,798,000
Common stock outstanding (in shares)	74,565,000	74,485,000
Common stock in treasury (in shares)	1,432,000	1,313,000