COPT Defense Properties Annual report pursuant to Section 13 and 15(d)

Annual report pursuant to Section 13 and 15(d)

Properties, net (Details 6)

Properties, net (Details 6) ft² in Thousands, $ in Thousands		12 Months Ended
	Aug. 28, 2015 USD ($)	Dec. 31, 2016 USD ($) ft² buillding Property	Dec. 31, 2015 USD ($) ft² buillding Property	Dec. 31, 2014 USD ($) ft² buillding Property
Dispositions
(Loss) gain on early extinguishment of debt		$ (1,110)	$ 85,275	$ (9,552)
Non-operating Properties [Member]
Dispositions
Gain on disposition			4,000	5,600
Sale price of non-operating properties			$ 18,100	$ 28,300
Operating properties, net [Member]
Dispositions
Number of Buildings \| buillding		21	9	8
Total Rentable Square Feet \| ft²		1,577	1,597	303
Transaction Value		$ 248,738	$ 347,785	$ 28,835
Gain on disposition		$ 15,871	$ 64,033	$ 5,093
15000 and 15010 Conference Center Drive [Member] \| Operating properties, net [Member]
Dispositions
Debt settled through the surrender of real estate assets	$ 150,000
(Loss) gain on early extinguishment of debt	$ 84,800
Regional Office [Member] \| Operating properties, net [Member] \| 1550 Westbranch Drive [Member]
Dispositions
Number of Buildings \| buillding			1
Total Rentable Square Feet \| ft²			160
Transaction Value			$ 27,800
Gain on disposition			$ 0
Regional Office [Member] \| Operating properties, net [Member] \| 13200 Woodland Park Road [Member]
Dispositions
Number of Buildings \| buillding			1
Total Rentable Square Feet \| ft²			397
Transaction Value			$ 84,000
Gain on disposition			$ 42,515
Regional Office [Member] \| Operating properties, net [Member] \| 9900, 9910, 9920 Franklin Square Drive [Member]
Dispositions
Number of Buildings \| buillding			3
Total Rentable Square Feet \| ft²			135
Transaction Value			$ 24,150
Gain on disposition			$ 6,468
Regional Office [Member] \| Operating properties, net [Member] \| 9690 Deereco Road and 375 W Padonia Road [Member]
Dispositions
Number of Buildings \| buillding			2
Total Rentable Square Feet \| ft²			240
Transaction Value			$ 44,500
Gain on disposition			$ 15,050
Regional Office [Member] \| Operating properties, net [Member] \| 4969 and 4979 Mercantile Rd [Member]
Dispositions
Number of Buildings \| buillding				2
Total Rentable Square Feet \| ft²				97
Transaction Value				$ 5,960
Gain on disposition				$ 2,124
Regional Office [Member] \| Operating properties, net [Member] \| 9930 and 9940 Franklin Square [Member]
Dispositions
Number of Buildings \| buillding				2
Total Rentable Square Feet \| ft²				72
Transaction Value				$ 10,475
Gain on disposition				$ 2,303
Regional Office [Member] \| Operating properties, net [Member] \| 5020, 5022, 5024 and 5026 Campbell Boulevard [Member]
Dispositions
Number of Buildings \| buillding				4
Total Rentable Square Feet \| ft²				134
Transaction Value				$ 12,400
Gain on disposition				$ 666
Defense/Information Technology Sector [Member] \| Northern Virginia Defense/IT [Member] \| Operating properties, net [Member] \| 15000 and 15010 Conference Center Drive [Member]
Dispositions
Number of Buildings \| buillding			2
Total Rentable Square Feet \| ft²			665
Transaction Value			$ 167,335
Gain on disposition			$ 0
Newly-constructed properties placed in service [Member]
Dispositions
Square Feet of Properties Placed in Service \| ft²		639	897	692
Number of real estate properties \| Property		6	7	5
Newly Redeveloped Properties Placed In Service [Member]
Dispositions
Square Feet of Properties Placed in Service \| ft²		61
Number of real estate properties \| Property		3
Newly Redeveloped Properties Placed In Service [Member] \| Greater Philadelphia and St. Mary's County, Maryland [Member]
Dispositions
Square Feet of Properties Placed in Service \| ft²			170
Number of real estate properties \| Property			2
Properties under Construction or Contractually Commited for Construction [Member]
Dispositions
Total Rentable Square Feet \| ft²		1,300
Number of real estate properties \| Property		8
Properties under redevelopment [Member]
Dispositions
Total Rentable Square Feet \| ft²		104
Number of real estate properties \| Property		3
Office properties under, or contractually committed for, construction or approved for redevelopment [Member]
Dispositions
Total Rentable Square Feet \| ft²		1,400
Number of real estate properties \| Property		11
Office properties under, or contractually committed for, construction or approved for redevelopment [Member] \| Properties completed Held-for-future lease [Member]
Dispositions
Number of real estate properties \| Property		2
Office properties under, or contractually committed for, construction or approved for redevelopment [Member] \| Partially operational properties [Member]
Dispositions
Number of real estate properties \| Property		2