The difference between the carrying value and the sale price of real estate or properties that were intended to be sold or held for capital appreciation or rental income. This element refers to the gain (loss) included in earnings and not to the cash proceeds of the sale. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3602-108585

Name:	us-gaap_GainLossOnSaleOfProperties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Subsequent Event (Details) ft² in Thousands, $ in Thousands		9 Months Ended
Subsequent Event (Details) ft² in Thousands, $ in Thousands	Oct. 27, 2015 USD ($) ft²	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)
Subsequent Event [Line Items]
Gain on sale		$ 4,000	$ 10,654
Subsequent Event \| Northern Virginia \| 13200 Woodland Park Rd
Subsequent Event [Line Items]
Square footage of real estate properties (in square feet) \| ft²	397
Transaction value of operating property disposition	$ 84,000
Gain on sale	$ 42,000