Quarterly Results (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 131,529	$ 131,693	$ 134,631	$ 137,171	$ 134,153	$ 135,421	$ 130,668	$ 132,936	$ 535,024	$ 533,178	$ 525,967
Gain/(loss) on sale of real estate assets	14,634	(340)	191,369	3	157,640	32	1,451	37,887	205,666	197,010	75,691
Net income	22,608	8,940	192,426	8,711	162,476	8,419	8,152	50,209	232,685	229,256	130,291
Net income applicable to Piedmont	$ 22,609	$ 8,943	$ 192,427	$ 8,709	$ 162,478	$ 8,422	$ 8,153	$ 50,208	$ 232,688	$ 229,261	$ 130,296
Basic earnings per share (in dollars per share)	$ 0.18	$ 0.07	$ 1.53	$ 0.07
Diluted earnings per share (in dollars per share)	0.18	0.07	1.52	0.07
Basic and diluted earnings per share (in dollars per share)					$ 1.29	$ 0.07	$ 0.06	$ 0.40	$ 1.85	$ 1.82	$ 1.00
Dividends declared (in dollars per share)	$ 0.21	$ 0.21	$ 0.21	$ 0.21	$ 0.21	$ 0.21	$ 0.21	$ 0.21