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Fair Value - Information about Significant Unobservable Inputs (Parenthetical) (Detail) - EUR (€)
€ in Millions
Dec. 31, 2018
Dec. 31, 2017
Derivatives [member] | Level III [member]    
Disclosure of significant unobservable inputs used in fair value measurement of assets and liabilities [line items]    
Investments for account of policyholders € 2 € 3