CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
CONSOLIDATED STATEMENTS OF OPERATIONS
REVENUE	$ 3,073,636	$ 2,856,659	$ 2,615,277
COST OF SERVICES	2,510,429	2,309,676	2,113,334
Gross profit	563,207	546,983	501,943
SELLING, GENERAL AND ADMINISTRATIVE EXPENSES	376,309	357,777	340,005
GAIN ON SALE OF ASSETS	(1,540)	(1,445)	(1,701)
Operating income	188,438	190,651	163,639
OTHER INCOME (EXPENSE):
Interest income	24	103	224
Interest expense	(6,196)	(8,385)	(9,317)
Changes in the fair value of contingent earn-out obligations	7,820	9,119	(2,991)
Other	188	52	187
Other income (expense)	1,836	889	(11,897)
INCOME BEFORE INCOME TAXES	190,274	191,540	151,742
PROVISION FOR INCOME TAXES	46,926	41,401	37,418
NET INCOME	$ 143,348	$ 150,139	$ 114,324
INCOME PER SHARE:
Basic	$ 3.95	$ 4.11	$ 3.10
Diluted	$ 3.93	$ 4.09	$ 3.08
SHARES USED IN COMPUTING INCOME PER SHARE:
Basic	36,285	36,542	36,854
Diluted	36,450	36,738	37,131