CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Accounts receivable, reserve for credit losses	$ 75,426	$ 52,274
Property, equipment and capitalized software, accumulated depreciation	363,097	344,212
Accumulated amortization	$ 698,470	$ 666,793
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	175,000,000	175,000,000
Common stock, shares issued (in shares)	47,938,000	47,749,000
Common stock, shares outstanding (in shares)	43,510,000	43,321,000
Treasury stock, shares (in shares)	4,428,000	4,428,000