Unaudited Consolidated Statements of Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Statement [Abstract]
Revenues, net	$ 183,033	$ 167,036
Cost of revenues (exclusive of depreciation and amortization)	120,119	108,379
Gross profit	62,914	58,657
Operating expenses:
General and administrative expenses	24,224	20,618
Selling and marketing expenses	13,362	13,454
Depreciation and amortization	9,426	8,133
Total operating expenses	47,012	42,205
Income from operations	15,902	16,452
Foreign exchange gain, net	1,568	469
Interest expense	(432)	(385)
Other income, net	3,310	3,179
Income before income tax expense	20,348	19,715
Income tax expense	3,560	5,895
Net income	$ 16,788	$ 13,820
Earnings per share:
Basic (in dollars per share)	$ 0.50	$ 0.41
Diluted (in dollars per share)	$ 0.48	$ 0.40
Weighted-average number of shares used in computing earnings per share:
Basic weighted average common shares outstanding (in shares)	33,845,560	33,380,028
Diluted weighted average common shares outstanding (in shares)	35,108,882	34,351,657