Management Statement (Details)	Sep. 30, 2013 sqft item
Real estate properties
Properties owned	3,866
Number of U.S. states where properties are owned	49
Leasable square feet	61,200,000

The number of states the entity operates in as of the balance sheet date.

No definition available.

Name:	us-gaap_NumberOfStatesInWhichEntityOperates
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant