Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash flows from operating activities:
Net income (loss)	$ (4,381)	$ (31,004)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	16,279	21,647
Stock-based compensation expense	33,758	56,507
(Gain) loss from sales of investments, assets and other, net	(184)	242
Accretion and amortization on marketable securities		311
Change in deferred income taxes and other	2,268	1,570
Changes in operating assets and liabilities:
Accounts receivable, net	(7,968)	14,536
Income tax receivable	47	772
Other assets	(2,641)	(4,442)
Accounts payable	(8,341)	(14,316)
Deferred revenue	13,021	(12,178)
Income tax payable	2,749
Other liabilities	(11,496)	(22,404)
Net cash provided by (used in) operating activities	33,111	11,241
Cash flows from investing activities:
Sales and maturities of marketable securities		204,802
Acquisition of property and equipment	(4,141)	(3,947)
Business acquisitions, net of cash acquired	(35,081)	(14,220)
Proceeds from sale of property and equipment	148	1,577
Other investing activities, net	(7,225)
Net cash provided by (used in) investing activities	(46,299)	188,212
Cash flows from financing activities:
Taxes paid related to net share settlement of stockholders' equity awards	(9,423)	(1,665)
Repurchases of common stock	(96,924)	(112,392)
Proceeds from issuance of common stock	4,017	2,885
Net cash provided by (used in) financing activities	(102,330)	(111,172)
Effect of exchange rate changes on cash and cash equivalents	2,026	(2,110)
Net increase (decrease) in cash and cash equivalents	(113,492)	86,171
Cash and cash equivalents, beginning of period	852,467	742,217
Cash and cash equivalents, end of period	$ 738,975	$ 828,388