CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
CONSOLIDATED STATEMENTS OF OPERATIONS
REVENUE	$ 2,615,277	$ 2,182,879	$ 1,787,922
COST OF SERVICES	2,113,334	1,736,600	1,421,641
Gross profit	501,943	446,279	366,281
SELLING, GENERAL AND ADMINISTRATIVE EXPENSES	340,005	296,986	266,586
GOODWILL IMPAIRMENT			1,105
GAIN ON SALE OF ASSETS	(1,701)	(945)	(670)
Operating income	163,639	150,238	99,260
OTHER INCOME (EXPENSE):
Interest income	224	73	70
Interest expense	(9,317)	(3,710)	(3,156)
Changes in the fair value of contingent earn-out obligations	(2,991)	(2,066)	3,715
Other	187	4,141	1,049
Other income (expense)	(11,897)	(1,562)	1,678
INCOME BEFORE INCOME TAXES	151,742	148,676	100,938
PROVISION FOR INCOME TAXES	37,418	35,773	45,666
NET INCOME	$ 114,324	$ 112,903	$ 55,272
INCOME PER SHARE:
Basic (in shares)	$ 3.10	$ 3.03	$ 1.48
Diluted (in shares)	$ 3.08	$ 3.00	$ 1.47
SHARES USED IN COMPUTING INCOME PER SHARE:
Basic (in shares)	36,854	37,202	37,239
Diluted (in shares)	37,131	37,592	37,672
DIVIDENDS PER SHARE (in dollars per share)	$ 0.395	$ 0.330	$ 0.295