Commitments and Contingencies (Textual) (Details)			9 Months Ended	12 Months Ended
	Dec. 03, 2015 ft²	Apr. 02, 2015 USD ($)	Sep. 30, 2004 USD ($)	Dec. 31, 2016 USD ($) ft² a	Jan. 31, 2017	Jan. 30, 2017 a	Jul. 01, 2016 USD ($) a	Dec. 31, 2015 USD ($)
Property Subject to or Available for Operating Lease [Line Items]
Real estate ventures aggregate indebtedness to third parties				$ 997,466,000				$ 794,571,000
Agreed holding period (not to sell) for properties acquired as part of the TRC acquisition				15 years
Subaru Corporate Headquarters Project [Member]
Property Subject to or Available for Operating Lease [Line Items]
NTE Amount				$ 78,100,000
Subaru Build-to-Service Center Project [Member]
Property Subject to or Available for Operating Lease [Line Items]
Lease terms	18 years
Rentable Square Feet | ft²	83,000
Purchase option of lease from inception period	5 years
Project costs funded				10,500,000
Project costs				29,300,000
Subsequent Event [Member] | Garza Land Sale [Member]
Property Subject to or Available for Operating Lease [Line Items]
Area of land under agreement to sell | a						1.7
TB-BDN Plymouth Apartments [Member]
Property Subject to or Available for Operating Lease [Line Items]
Guarantees, maximum exposure amount				3,200,000
Construction Loan				56,000,000
TB-BDN Plymouth Apartments [Member] | Subsequent Event [Member]
Property Subject to or Available for Operating Lease [Line Items]
Sale of ownership interest percentage					50.00%
1919 Venture [Member]
Property Subject to or Available for Operating Lease [Line Items]
Guarantees, maximum exposure amount				88,900,000
Unconsolidated Real Estate Ventures [Member]
Property Subject to or Available for Operating Lease [Line Items]
Real estate ventures aggregate indebtedness to third parties				997,466,000
PJP VII [Member]
Property Subject to or Available for Operating Lease [Line Items]
Real estate ventures aggregate indebtedness to third parties				4,956,000				5,621,000
Guarantees, maximum exposure amount				400,000
618 Market Street [Member]
Property Subject to or Available for Operating Lease [Line Items]
Contingent consideration, liability		$ 2,000,000		$ 1,700,000
Fair value of contingent consideration		1,600,000
Interest expense		$ 2,000,000
Garza Land Acquisition [Member]
Property Subject to or Available for Operating Lease [Line Items]
Acreage of land | a							34.6
Area of land under agreement to sell | a				9.5
Infrastructure improvements to land, estimated cost							$ 10,300,000
Two Logan Square [Member]
Property Subject to or Available for Operating Lease [Line Items]
Leased Area Of Building | ft²				708,844
Amount to be paid if the Company takes fee title to Two Logan Square upon foreclosure of related mortgage				$ 2,900,000
Liability related to acquisition of TRC			$ 700,000	$ 2,200,000
Commerce Square [Member] | Prentiss Properties Trust [Member]
Property Subject to or Available for Operating Lease [Line Items]
Non-controlling interest, ownership percentage by non-controlling Owners				1.00%
One Commerce Square [Member]
Property Subject to or Available for Operating Lease [Line Items]
Tax guarantee obligation				$ 125,000,000
Two Commerce Square [Member]
Property Subject to or Available for Operating Lease [Line Items]
Tax guarantee obligation				100,000,000
Put Agreement [Member]
Property Subject to or Available for Operating Lease [Line Items]
Purchase price				$ 35,000,000
Minimum [Member]
Property Subject to or Available for Operating Lease [Line Items]
Lease terms				4 years
Maximum [Member]
Property Subject to or Available for Operating Lease [Line Items]
Lease terms				72 years
Mortgage Lenders [Member]
Property Subject to or Available for Operating Lease [Line Items]
Associated letter of credit				$ 10,000,000				$ 10,000,000