Consolidated Statement of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
OPERATING ACTIVITIES:
Net income (loss)	$ 2,284	$ (5,031)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	8,626	4,390
Stock-based compensation	8,391	5,498
Loss on disposal of property and equipment, net	3	28
Change in fair value of contingent consideration	0	138
Unrealized foreign currency (gains) losses, net	972	(1,054)
Deferred Income Taxes and Tax Credits	(4,351)	0
Changes in operating assets and liabilities:
Accounts receivable	59,303	12,227
Prepaid expenses and other assets	179	1,471
Accounts payable and accrued expenses	(64,180)	5,564
Other liabilities	(559)	(795)
Net cash provided by operating activities	10,668	22,436
INVESTING ACTIVITIES:
Purchases of property and equipment, net	(1,443)	(2,259)
Capitalized internal use software development costs	(2,306)	(2,116)
Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities	6,400	0
Change in restricted cash	0	1,252
Net cash provided (used) by investing activities	2,651	(3,123)
FINANCING ACTIVITIES:
Proceeds from exercise of stock options	6,718	4,031
Repayment of debt and capital lease obligations	0	(52)
Net cash provided by financing activities	6,718	3,979
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	31	(152)
CHANGE IN CASH AND CASH EQUIVALENTS	20,068	23,140
CASH AND CASH EQUIVALENTS--Beginning of period	116,499	97,196
CASH AND CASH EQUIVALENTS--End of period	136,567	120,336
SUPPLEMENTAL DISCLOSURES OF OTHER CASH FLOW INFORMATION:
Capitalized assets financed by accounts payable and accrued expenses	667	448
Capitalized stock-based compensation	$ 206	$ 172