Commitments to Acquire/Dispose of Real Estate (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012
Commitments to Acquire Real Estate
Properties Acquired-Total	2
Land Parcels Contracted to be Acquired	2
Rental Units Acquired - Total	542
Purchase Price - Total	$ 249,750
Commitments to Dispose of Real Estate
Properties Disposed - Total	5
Rental Units Disposed-Total	1,578
Sales price-Rental Properties	141,450
Rental Properties to be acquired [Member]
Commitments to Acquire Real Estate
Properties Acquired-Total	2
Rental Units Acquired - Total	542
Purchase Price - Total	192,250
Land Parcel [Member]
Commitments to Acquire Real Estate
Land Parcels Contracted to be Acquired	0
Rental Units Acquired - Total	0
Purchase Price - Total	57,500
Rental Properties Disposed of [Member]
Commitments to Dispose of Real Estate
Properties Disposed - Total	5
Rental Units Disposed-Total	1,578
Sales price-Rental Properties	$ 141,450