Subsequent Events (Details) (Oaklands Corporate Center [Member], USD $) In Millions, unless otherwise specified	Jul. 18, 2012 sqft Properties
Oaklands Corporate Center [Member]
Subsequent Event [Line Items]
Number of Properties Sold	11
Net Rentable Space	466,719
Sale Consideration Of Sold Property	$ 52.7

Number of Properties Sold Subsequent to Balance Sheet Date

No definition available.

Name:	bdn_NumberOfPropertiesSoldSubsequentToBalanceSheetDate
Namespace Prefix:	bdn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant