Note 13 - Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block]

	Years ended December 31,
		2018		2017		2016
Cost of services-compensation	$	7,421	$	7,354	$	3,805
Selling, general and administrative		14,086		16,789		9,472
Total	$	21,507	$	24,143	$	13,277

Share-based Compensation, Stock Options, Activity [Table Text Block]

	Number of Options			Weighted Average Exercise Price	Weighted Average- Remaining Contractual Terms		Aggregate- Intrinsic Value
Outstanding balance at December 31, 2017	5,554		$	17.35
Granted	1,010			19.58
Exercised	(2,017	)		19.14
Forfeitures	(114	)		17.74
Expired	(31	)		22.34
Outstanding balance at December 31, 2018	4,402			17.07	5.80	$	48,339
Expected to vest at December 31, 2018	1,481		$	18.60	8.22	$	14,119
Exercisable at December 31, 2018	2,370		$	15.87	3.83	$	29,068

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	Year ended December 31,
		2018		2017		2016
Expected dividend yield		-		-		-
Risk-free interest rate		2.7	%	1.8	%	1.2	%
Expected volatility		42.4	%	44.2	%	44.0	%
Expected life (years)		6.0		5.0		4.9

	Year ended December 31,
		2018	2017		2016
Expected dividend yield		-	-		-
Risk-free interest rate		-	2.2	%	1.6	%
Expected volatility		-	52.5	%	40.5	%
Expected life (years)		-	6.5		4.9

Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]

	Number of Units			Weighted Average Grant Date Fair Value per Unit
Outstanding balance at December 31, 2017		1,346		$	17.65
Granted		766			16.80
Vesting of restricted stock units, net of units withheld for taxes		(371	)		17.06
Units withheld for taxes		(163	)		17.06
Forfeitures		(90	)		17.31
Outstanding balance at December 31, 2018		1,488		$	17.60