Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Accounts receivable, allowance	$ 8,511	$ 3,332
Accumulated depreciation - fixed assets	153,390	132,900
Accumulated amortization	$ 199,488	$ 151,417
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	49,550,000	49,283,000
Common stock, shares outstanding (in shares)	46,989,000	46,722,000
Treasury stock (in shares)	2,561,000	2,561,000