Schedule of Estimated Lives of Assets (Detail)	3 Months Ended
Mar. 31, 2013
Property, Plant, and Equipment Disclosure [Line Items]
Tenant improvements	Shorter of the useful lives or the terms of the related leases
Maximum
Property, Plant, and Equipment Disclosure [Line Items]
Building and improvements	40 years
Minimum
Property, Plant, and Equipment Disclosure [Line Items]
Building and improvements	15 years

Describes the periods of time over which an entity anticipates to receive utility from its property, plant and equipment (that is, the periods of time over which an entity allocates the initial cost of its property, plant and equipment).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6367646&loc=d3e18780-107790

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-URI http://asc.fasb.org/subtopic&trid=2155824

Name:	us-gaap_PropertyPlantAndEquipmentEstimatedUsefulLives
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration