Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net income (loss)	$ 13,710	$ (72,741)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	23,889	32,158
Stock-based compensation expense	49,346	80,982
(Gain) loss from sales of investments, assets and other, net	(206)	160
Accretion and amortization on marketable securities	(172)	322
Change in deferred income taxes and other	4,222	(2,734)
Impairment of intangible assets		20,677
Changes in operating assets and liabilities:
Accounts receivable, net	(12,150)	8,743
Income tax receivable	65	1,711
Other assets	294	(2,519)
Accounts payable	(6,012)	(10,171)
Deferred revenue	1,913	2,121
Income tax payable	2,003
Other liabilities	(8,705)	(26,436)
Net cash provided by (used in) operating activities	68,197	32,273
Cash flows from investing activities:
Purchases of marketable securities	(255,301)
Sales and maturities of marketable securities		240,337
Acquisition of property and equipment	(6,878)	(6,621)
Business acquisitions, net of cash acquired	(35,081)	(33,630)
Proceeds from sale of property and equipment	221	3,035
Other investing activities, net	(7,225)
Net cash provided by (used in) investing activities	(304,264)	203,121
Cash flows from financing activities:
Taxes paid related to net share settlement of stockholders' equity awards	(14,576)	(2,163)
Repurchases of common stock	(96,924)	(112,392)
Proceeds from issuance of common stock	8,249	5,570
Net cash provided by (used in) financing activities	(103,251)	(108,985)
Effect of exchange rate changes on cash and cash equivalents	4,108	(2,307)
Net increase (decrease) in cash and cash equivalents	(335,210)	124,102
Cash and cash equivalents, beginning of period	852,467	742,217
Cash and cash equivalents, end of period	$ 517,257	$ 866,319