CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Accounts receivable, allowance	$ 2,166	$ 1,696
Contract assets, allowance	376	359
Property and equipment, accumulated depreciation	313,999	294,366
Intangible assets, accumulated amortization	$ 16,201	$ 14,467
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	4,000,000	4,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	16,869,947	16,734,239
Common stock, shares outstanding (in shares)	16,869,947	16,734,239