CONSOLIDATED STATEMENTS OF INCOME AND COMPREHENSIVE INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Income Statement [Abstract]
Revenues	$ 914,128		$ 730,027		$ 555,117
Operating expenses:
Cost of revenues (exclusive of depreciation and amortization)	566,913		456,530		347,650
Selling, general and administrative expenses	222,759		163,666		116,497
Depreciation and amortization expense	17,395		17,483		15,120
Goodwill impairment loss	0		2,241		0
Other operating expenses/(income), net	1,094		3,924		(643)
Income from operations	105,967		86,183		76,493
Interest and other income, net	4,731		4,769		3,077
Change in fair value of contingent consideration	0		(1,924)		0
Foreign exchange loss	(4,628)		(2,075)		(2,800)
Income before provision for income taxes	106,070		86,953		76,770
Provision for income taxes	21,614		17,312		14,776
Net income	84,456		69,641		61,994
Foreign currency translation adjustments	(13,096)		(20,251)		(811)
Comprehensive income	$ 71,360		$ 49,390		$ 61,183
Net income per share:
Basic (in dollars per share)	$ 1.73	[1]	$ 1.48	[2]	$ 1.35
Diluted (in dollars per share)	$ 1.62	[1]	$ 1.40	[2]	$ 1.28
Shares used in calculation of net income per share:
Basic (in shares)	48,721		47,189		45,754
Diluted (in shares)	51,986		49,734		48,358

[1] (1)Earnings per share amounts for each quarter may not necessarily total to the yearly earnings per share due to the weighting of shares outstanding on a quarterly and year to date basis.

[2] (1)Earnings per share amounts for each quarter may not necessarily total to the yearly earnings per share due to the weighting of shares outstanding on a quarterly and year to date basis.