Components of Rental Income and Expense - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Rental Income [Line Items]
Recognition of straight-line rents	$ 7.2	$ 4.8
Recognition of amortization of above and below market leases	$ (0.2)	$ (1.1)	$ (1.1)

Difference between actual rental income due and rental income recognized on a straight-line basis.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

Name:	us-gaap_StraightLineRent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration