Consolidated Statements of Income (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Income Statement [Abstract]
Revenues	$ 122,457	$ 122,315	$ 363,992	$ 354,329
Cost of revenues (exclusive of depreciation and amortization)	84,983	72,049	241,164	218,892
Gross profit	37,474	50,266	122,828	135,437
Operating expenses:
General and administrative expenses	15,952	15,791	46,992	44,265
Selling and marketing expenses	9,117	8,993	28,812	27,884
Depreciation and amortization	7,014	5,969	20,049	18,843
Total operating expenses	32,083	30,753	95,853	90,992
Income from operations	5,391	19,513	26,975	44,445
Other income/(expense) :
Foreign exchange income/(loss)	642	(2,508)	(328)	(3,126)
Interest and other income, net	1,044	465	2,861	1,761
Income before income taxes	7,077	17,470	29,508	43,080
Income tax provision	1,002	4,230	4,523	10,842
Net income	$ 6,075	$ 13,240	$ 24,985	$ 32,238
Earnings per share:
Basic	$ 0.18	$ 0.40	$ 0.76	$ 0.98
Diluted	$ 0.18	$ 0.39	$ 0.74	$ 0.95
Weighted-average number of shares used in computing earnings per share:
Basic	32,890,475	32,907,281	32,743,384	32,737,267
Diluted	33,676,665	33,955,445	33,594,304	33,859,525