Real Estate and Lending Activities - Loans - Additional Information (Detail) € in Millions	Mar. 31, 2019 EUR (€)
Primotop Holdings S.a.r.l. [Member]
Loans [Line Items]
Shareholder loan to joint venture	€ 290

For an unclassified balance sheet, amounts due from an entity in which the reporting entity shares joint control with another party or group.

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Name:	us-gaap_DueFromJointVentures
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant