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Fair Value of Financial Instruments (Details Textuals) (Details) (Variable rate and mortgage debt [Member])
3 Months Ended
Mar. 31, 2015
Variable rate and mortgage debt [Member]
 
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]  
Weighted average discount rate 4.70%us-gaap_FairValueInputsDiscountRate
/ us-gaap_FinancialInstrumentAxis
= bdn_VariablerateandmortgagedebtMember