Subsequent Events (Parenthetical) (Detail)	9 Months Ended
Sep. 30, 2013 Property
Numberof Buildings Acquired [Roll Forward]
Number of properties acquired	71us-gaap_NumberOfBusinessesAcquired

The number of businesses acquired by the entity during the period.

No definition available.

Name:	us-gaap_NumberOfBusinessesAcquired
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration