Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Current assets:
Accounts receivable, allowance for doubtful accounts	$ 5,271	$ 4,255
Noncurrent assets:
Property and equipment, accumulated depreciation	149,759	130,320
Customer relationships and other intangible assets, accumulated amortization	$ 89,939	$ 81,656
Stockholders' equity:
Common stock, par value (in usd per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	31,718,589	31,507,247
Common stock, shares outstanding (in shares)	25,951,489	26,229,809
Treasury stock, shares (in shares)	5,767,100	5,277,438