Business (Details)	Mar. 31, 2013 Number properties
Business (Details) [Abstract]
Number of properties in diversified portfolio	1,133
Number of states in diversified portfolio	46

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