Discontinued Operations - Financial Statement Information (Details) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income tax expense					$ 0	$ 2,900	$ 22,737
(Loss) income from discontinued operations, net of income tax	$ 0	$ 0	$ 0	$ (42,704)	0	(42,704)	66,257
Separation costs						500	2,500
Cumulative-effect adjustment from adoption of accounting standards					132,778	388
Spinoff transaction						461,831
Transfer of cash					0	28,523	0
GoTo Business Division
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net revenues						58,215	682,185
Cost of net revenues						15,456	154,652
Gross margin						42,759	527,533
Research and development						9,108	93,892
Sales, marketing and services						20,881	209,475
General and administrative						7,636	63,270
Amortization of other intangible assets						1,176	14,097
Restructuring						3,189	3,721
Separation						40,573	54,084
Total operating expenses						82,563	438,539
(Loss) income from discontinued operations before income taxes						(39,804)	88,994
Income tax expense						2,900	22,737
(Loss) income from discontinued operations, net of income tax						(42,704)	$ 66,257
Retained Earnings
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cumulative-effect adjustment from adoption of accounting standards					$ 132,778	(5,303)
Spinoff transaction						475,231
Foreign currency | GoTo Business Division
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Distribution of the GoTo Business						$ 13,400