CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
CURRENT ASSETS:
Trade receivables, allowances	$ 5,953	$ 5,313
STOCKHOLDERS' EQUITY:
Preferred stock shares authorized (in shares)	5,000	5,000
Preferred stock shares issued (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0	$ 0
Common stock shares authorized (in shares)	100,000	100,000
Common stock shares issued (in shares)	55,933	55,623
Common stock shares outstanding (in shares)	55,933	55,623
Developed technology
OTHER ASSETS:
Intangibles, accumulated amortization	$ 203,308	$ 193,164
Other
OTHER ASSETS:
Intangibles, accumulated amortization	$ 59,025	$ 56,943