Fair Value of Financial Instruments Fair Value of Financial Instruments (Details Textuals) (Details)	Mar. 31, 2013
Fair Value Disclosures [Abstract]
Weighted Average Fair Value Interest Rate on Debt	3.199%

Weighted Average Fair Value Interest Rate on Debt Unobservable Input Fair Value Intererest Rates

No definition available.

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Namespace Prefix:	bdn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant