Acquisitions and Dispositions (Narrative) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($) buildings	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) buildings	Sep. 30, 2015 USD ($)
Number Of Real Estate Properties Acquired | buildings	2		2
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life			8 years 10 months 24 days
Operating Leases, Income Statement, Lease Revenue	$ 206,848,000	$ 200,938,000	$ 609,171,000	$ 617,549,000
Operating Income (Loss)	152,453,000	119,703,000	380,377,000	389,169,000
Property, Plant, and Equipment, Fair Value Disclosure	72,824,000		72,824,000
Gain on dissolution of unconsolidated company	0	0	30,697,000	0
Promote income	$ 2,212,000	$ 0	$ 26,299,000	$ 0
Duke Realty Limited Partnership [Member]
Number Of Real Estate Properties Acquired | buildings	1		1
Property, Plant, and Equipment, Fair Value Disclosure	$ 63,000,000		$ 63,000,000
Proceeds from Equity Method Investment, Dividends or Distributions			2,760,000
Equity Method Investments	$ (35,063,000)		(35,063,000)
Gain on dissolution of unconsolidated company			30,697,000
Other 2016 Acquisitions [Member]
Operating Leases, Income Statement, Lease Revenue			2,100,000
Operating Income (Loss)			$ (28,000)
Gramercy Property Trust [Member]
Number of Real Estate Properties | buildings	7		7
Duke/Hulfish LLC [Member]
Number of Real Estate Properties | buildings	8		8
Duke/Hulfish LLC [Member]
Equity Method Investment, Ownership Percentage	20.00%		20.00%