Business - Ownership Breakdown (Details)	Dec. 31, 2017 Property ApartmentUnit
Property/Unit schedule
Properties | Property	305
Apartment Units | ApartmentUnit	78,611
Wholly Owned Properties
Property/Unit schedule
Properties | Property	283
Apartment Units | ApartmentUnit	73,598
Master-Leased Properties – Consolidated
Property/Unit schedule
Properties | Property	3
Apartment Units | ApartmentUnit	853
Partially Owned Properties – Consolidated
Property/Unit schedule
Properties | Property	17
Apartment Units | ApartmentUnit	3,215
Partially Owned Properties – Unconsolidated
Property/Unit schedule
Properties | Property	2
Apartment Units | ApartmentUnit	945