Consolidated Balance Sheets (Parenthetical) - USD ($)	Mar. 31, 2021	Dec. 31, 2020
Stockholders' equity
Accounts Receivable, Allowance for Credit Loss, Current	$ 4,997,000	$ 5,067,000
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	150,000,000	150,000,000
Common stock, shares outstanding	46,819,468	46,737,033
Treasury stock, shares	35,232,785	35,315,220