CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
CONSOLIDATED STATEMENTS OF OPERATIONS
REVENUE	$ 2,182,879	$ 1,787,922	$ 1,634,340
COST OF SERVICES	1,736,600	1,421,641	1,290,331
Gross profit	446,279	366,281	344,009
SELLING, GENERAL AND ADMINISTRATIVE EXPENSES	296,986	266,586	243,201
GOODWILL IMPAIRMENT		1,105
GAIN ON SALE OF ASSETS	(945)	(670)	(761)
Operating income	150,238	99,260	101,569
OTHER INCOME (EXPENSE):
Interest income	73	70	9
Interest expense	(3,710)	(3,156)	(2,345)
Changes in the fair value of contingent earn-out obligations	(2,066)	3,715	731
Other	4,141	1,049	1,097
Other income (expense)	(1,562)	1,678	(508)
INCOME BEFORE INCOME TAXES	148,676	100,938	101,061
PROVISION FOR INCOME TAXES	35,773	45,666	36,165
NET INCOME	$ 112,903	$ 55,272	$ 64,896
INCOME PER SHARE:
Basic (in shares)	$ 3.03	$ 1.48	$ 1.74
Diluted (in shares)	$ 3.00	$ 1.47	$ 1.72
SHARES USED IN COMPUTING INCOME PER SHARE:
Basic (in shares)	37,202	37,239	37,335
Diluted (in shares)	37,592	37,672	37,811
DIVIDENDS PER SHARE (in dollars per share)	$ 0.330	$ 0.295	$ 0.275