Commitments and Contingencies (Textual) (Details)			3 Months Ended
	Dec. 03, 2015 ft²	Apr. 02, 2015 USD ($)	Mar. 31, 2017 USD ($) a	Jul. 01, 2016 USD ($) a
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			10,800,000
Project costs			44,300,000
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			953,800,000
evo at Cira Centre South Venture [Member]
Property Subject to or Available for Operating Lease [Line Items]
Guarantees, maximum exposure amount			55,400,000
PJP VII [Member]
Property Subject to or Available for Operating Lease [Line Items]
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	$ 1,800,000
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			8.4
Area of land sold | a			1.7
Infrastructure improvements to land, estimated cost				$ 13,600,000
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