Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Allowance for doubtful accounts, current	$ 43,419	$ 47,209
Accumulated amortization of other intangible assets	19,299	17,216
Allowance for doubtful accounts, noncurrent	$ 10,000	$ 10,000
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)	75,519,000	75,344,000
Common stock outstanding (in shares)	74,112,000	73,877,000
Common stock in treasury (in shares)	1,407,000	1,467,000