Impairment Loss on Real Estate Assets (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment loss on real estate assets	[1]	$ 0	$ 10,950	$ 0	$ 10,950
Disposal Group, Held-for-sale, Not Discontinued Operations [Member] | 150 West Jefferson [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment loss on real estate assets	[2]	0	8,259	0	8,259
Disposal Group, Disposed of by Sale, Not Discontinued Operations [Member] | 9221 Corporate Boulevard [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Impairment loss on real estate assets	[3]	$ 0	$ 2,691	$ 0	2,691
Loss on impairment					$ 2,700

[1] The fair value measurements used in the evaluation of the non-financial assets above are considered to be Level 1 valuations within the fair value hierarchy as defined by GAAP, as there are direct observations and transactions involving the assets by unrelated, third-party purchasers.

[2] Piedmont recognized an impairment loss on real estate assets based upon the difference between the carrying value of the asset and the anticipated contract sales price, less estimated selling costs.

[3] Piedmont, using a probability-weighted model heavily weighted towards the short-term sale of the 9221 Corporate Boulevard building in Rockville, Maryland, determined that the carrying value would not be recovered from the undiscounted future operating cash flows expected from the use of the asset and its eventual disposition. As a result, Piedmont recognized a loss on impairment of approximately $2.7 million during the six months ended June 30, 2016 calculated as the difference between the carrying value of the asset and the anticipated contract sales price, less estimated selling costs.