Consolidated Statement of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
OPERATING ACTIVITIES:
Net income (loss)	$ (15,840)	$ 2,284
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	10,121	8,626
Stock-based compensation	6,239	8,391
Loss on disposal of property and equipment	258	3
Unrealized foreign currency gains, net	119	972
Deferred income taxes	282	(4,351)
Changes in operating assets and liabilities, net of effect of business acquisitions:
Accounts receivable	58,501	59,303
Prepaid expenses and other assets	(1,506)	179
Accounts payable and accrued expenses	(54,794)	(64,180)
Other liabilities	(499)	(559)
Net cash provided by operating activities	2,881	10,668
INVESTING ACTIVITIES:
Purchases of property and equipment	(3,084)	(1,443)
Capitalized internal use software development costs	(2,285)	(2,306)
Investments in available-for-sale securities	(14,948)	0
Maturities of available-for-sale securities	16,950	6,400
Net cash provided by (used in) investing activities	(3,367)	2,651
FINANCING ACTIVITIES:
Proceeds from exercise of stock options	368	6,718
Net cash provided by financing activities	368	6,718
EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS	62	31
CHANGE IN CASH AND CASH EQUIVALENTS	(56)	20,068
CASH AND CASH EQUIVALENTS — Beginning of period	149,423	116,499
CASH AND CASH EQUIVALENTS — End of period	149,367	136,567
SUPPLEMENTAL DISCLOSURES OF OTHER CASH FLOW INFORMATION:
Capitalized assets financed by accounts payable and accrued expenses	254	667
Capitalized stock-based compensation	$ 166	$ 206