Consolidated Statements of Cash Flows $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Operating Activities
Net (loss) income	$ (20,719)	$ 536,112	$ 319,361
Loss (income) from discontinued operations	42,704	(66,257)	(104,228)
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Amortization and impairment of intangible assets	82,878	70,494	224,750
Depreciation and amortization of property and equipment	87,137	107,954	102,207
Amortization of debt discount and transaction costs	38,298	37,085	36,013
Stock-based compensation expense	165,120	152,739	128,262
Deferred income tax expense (benefit)	94,158	(21,654)	(85,235)
Excess tax benefit from stock-based compensation	0	(16,049)	(5,873)
Effects of exchange rate changes on monetary assets and liabilities denominated in foreign currencies	(7,645)	5,189	13,815
Other non-cash items	11,924	8,618	6,767
Total adjustments to reconcile net (loss) income to net cash provided by operating activities	471,870	344,376	420,706
Changes in operating assets and liabilities, net of the effects of acquisitions:
Accounts receivable	(33,904)	(61,662)	(8,866)
Inventories	(2,545)	(4,133)	703
Prepaid expenses and other current assets	(18,327)	(12,077)	(10,257)
Other assets	2,116	(2,747)	(1,487)
Income taxes, net	318,795	42,431	48,675
Accounts payable	(7,238)	(16,365)	6,408
Accrued expenses and other current liabilities	34,886	22,650	49,662
Deferred revenues	174,426	142,381	102,330
Other liabilities	2,282	22,459	8,900
Total changes in operating assets and liabilities, net of the effects of acquisitions	470,491	132,937	196,068
Net cash provided by operating activities of continuing operations	964,346	947,168	831,907
Net cash (used in) provided by operating activities of discontinued operations	(56,070)	168,662	202,641
Net cash provided by operating activities	908,276	1,115,830	1,034,548
Investing Activities
Purchases of available-for-sale investments	(1,155,659)	(2,238,784)	(2,182,681)
Proceeds from sales of available-for-sale investments	775,135	1,294,636	1,745,290
Proceeds from maturities of available-for-sale investments	466,900	632,517	637,052
Purchases of property and equipment	(80,901)	(85,035)	(97,566)
Cash paid for acquisitions, net of cash acquired	(60,449)	(13,242)	(95,331)
Cash paid for licensing agreements and product related intangible assets	(7,379)	(25,940)	(10,795)
Other	2,323	1,181	5,209
Net cash (used in) provided by investing activities of continuing operations	(60,030)	(434,667)	1,178
Net cash used in investing activities of discontinued operations	(3,891)	(49,537)	(225,593)
Net cash used in investing activities	(63,921)	(484,204)	(224,415)
Financing Activities
Proceeds from issuance of common stock under stock-based compensation plans	2,114	41,247	112,285
Proceeds from revolving credit facility	165,000	0	95,000
Repayments on credit facility	(165,000)	0	(95,000)
Proceeds from 2027 notes, net of issuance costs	741,039	0	0
Repayment of acquired debt	(4,000)	0	(3,175)
Excess tax benefit from stock-based compensation	0	16,049	5,873
Stock repurchases, net	(1,174,957)	(28,689)	(755,704)
Accelerated stock repurchase program	(150,000)	0	0
Cash paid for tax withholding on vested stock awards	(80,040)	(66,638)	(46,336)
Transfer of cash to GoTo Business resulting from the separation	(28,523)	0	0
Net cash used in financing activities of continuing operations	(694,367)	(38,031)	(687,057)
Net cash used in financing activities of discontinued operations	0		(4,394)
Net cash used in financing activities	(694,367)	(38,031)	(691,451)
Effect of exchange rate changes on cash and cash equivalents	8,186	(5,157)	(10,313)
Change in cash and cash equivalents	158,174	588,438	108,369
Cash and cash equivalents at beginning of period, including cash of discontinued operations of $120,861, $57,762 and $34,651, respectively	956,956	368,518	260,149
Cash and cash equivalents at end of period	1,115,130	956,956	368,518
Less cash of discontinued operations	0	(120,861)	(57,762)
Cash and cash equivalents at end of period	1,115,130	836,095	310,756
Supplemental Cash Flow Information
Cash paid for income taxes	61,126	64,361	45,827
Cash paid for interest	$ 8,764	$ 7,847	$ 8,215