CONDENSED CONSOLIDATED STATEMENTS OF INCOME AND COMPREHENSIVE INCOME (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Statement [Abstract]
Revenues	$ 217,781	$ 174,695	$ 417,826	$ 335,079
Operating expenses:
Cost of revenues (exclusive of depreciation and amortization)	134,256	110,102	260,143	212,556
Selling, general and administrative expenses	55,976	38,671	102,914	71,030
Depreciation and amortization expense	3,903	5,451	8,103	9,140
Other operating expenses, net	40	1,995	240	2,020
Income from operations	23,606	18,476	46,426	40,333
Interest and other income, net	1,299	1,164	2,457	2,140
Foreign exchange loss	(465)	(1,239)	(6,219)	(2,480)
Income before provision for income taxes	24,440	18,401	42,664	39,993
Provision for income taxes	5,209	3,587	8,719	7,815
Net income	19,231	14,814	33,945	32,178
Foreign currency translation adjustments	3,674	2,894	944	(683)
Comprehensive income	$ 22,905	$ 17,708	$ 34,889	$ 31,495
Net income per share:
Basic (in dollars per share)	$ 0.40	$ 0.31	$ 0.70	$ 0.69
Diluted (in dollars per share)	$ 0.37	$ 0.30	$ 0.66	$ 0.65
Shares used in calculation of net income per share:
Basic (in shares)	48,584	47,068	48,237	46,933
Diluted (in shares)	51,917	49,559	51,461	49,384