Commitments to Acquire/Dispose of Real Estate (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012
Commitments to Acquire Real Estate
Properties Acquired-Total	5
Land Parcels Contracted to be Acquired	5
Rental Units Acquired - Total	708
Purchase Price - Total	$ 343,983
Commitments to Dispose of Real Estate
Properties Disposed - Total	8
Rental Units Disposed-Total	2,177
Sales price-Rental Properties	274,030
Rental Properties to be acquired [Member]
Commitments to Acquire Real Estate
Properties Acquired-Total	5
Rental Units Acquired - Total	708
Purchase Price - Total	231,983
Land Parcel [Member]
Commitments to Acquire Real Estate
Land Parcels Contracted to be Acquired	0
Rental Units Acquired - Total	0
Purchase Price - Total	112,000
Rental Properties Disposed of [Member]
Commitments to Dispose of Real Estate
Properties Disposed - Total	8
Rental Units Disposed-Total	2,177
Sales price-Rental Properties	$ 274,030