Business - Ownership Breakdown (Details)	Mar. 31, 2018 Property ApartmentUnit
Property/Unit schedule
Properties | Property	303
Apartment Units | ApartmentUnit	78,399
Wholly Owned Properties
Property/Unit schedule
Properties | Property	282
Apartment Units | ApartmentUnit	73,160
Master-Leased Properties – Consolidated
Property/Unit schedule
Properties | Property	2
Apartment Units | ApartmentUnit	759
Partially Owned Properties – Consolidated
Property/Unit schedule
Properties | Property	17
Apartment Units | ApartmentUnit	3,535
Partially Owned Properties – Unconsolidated
Property/Unit schedule
Properties | Property	2
Apartment Units | ApartmentUnit	945