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Intangible Assets, net - Additional Information (Detail) - USD ($)
3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Mar. 31, 2020
Jun. 30, 2021
Jun. 30, 2020
Indefinite-lived Intangible Assets [Line Items]          
Amortization of website development costs and intangible assets included in technology and development $ 13,400,000 $ 13,100,000   $ 26,300,000 $ 24,900,000
Non-cash impairment charge       0 76,800,000
Indefinite-lived intangible asset 108,000,000.0     108,000,000.0  
Fair value of the intangible asset $ 36,500,000     $ 36,500,000  
Trade names and trademarks | Trulia          
Indefinite-lived Intangible Assets [Line Items]          
Non-cash impairment charge     $ 71,500,000   $ 71,500,000
Useful life       10 years