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Segment Information - Summary of Investments (Parenthetical) (Detail) - Sony Life [member] - JP [member]
€ in Billions
12 Months Ended
Dec. 31, 2019
EUR (€)
Disclosure Of Summarized Investment Per Segment [line items]  
Off balance sheet investment in joint venture € 2.3
Potential Divestment In Associate [member]  
Disclosure Of Summarized Investment Per Segment [line items]  
Percentage of divestment in joint venture 50.00%