Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 92,100	$ 86,886
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	475,000,000	475,000,000
Common stock, shares issued (in shares)	126,944,155	126,448,078
Common stock, shares outstanding (in shares)	82,595,087	83,666,163
Treasury stock, shares (in shares)	44,349,068	42,781,915