Income Taxes - Narrative (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Mar. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Schedule Of Income Tax [Line Items]
Income tax benefit (expense)		$ (425)	$ 1,300	$ 8,124	$ 3,800
Non-cash impairment charge				76,800	$ 0
Trulia | Trade names and trademarks
Schedule Of Income Tax [Line Items]
Income tax benefit (expense)				9,700
Non-cash impairment charge	$ 71,500			$ 71,500
Federal
Schedule Of Income Tax [Line Items]
Net operating loss carryforwards						$ 1,137,600
State
Schedule Of Income Tax [Line Items]
Net operating loss carryforwards						$ 34,300