Quarterly Results (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 134,153	$ 135,421	$ 130,668	$ 132,936	$ 137,185	$ 129,708	$ 129,174	$ 129,900	$ 533,178	$ 525,967	$ 574,173
Gain/(loss) on sale of real estate assets	157,640	32	1,451	37,887	30,505	0	(23)	45,209	197,010	75,691	115,874
Net income	162,476	8,419	8,152	50,209	45,409	16,114	10,940	57,828	229,256	130,291	133,549
Net income/(loss) applicable to Piedmont	$ 162,478	$ 8,422	$ 8,153	$ 50,208	$ 45,410	$ 16,114	$ 10,942	$ 57,830	$ 229,261	$ 130,296	$ 133,564
Basic and diluted earnings per share (in dollars per share)	$ 1.29	$ 0.07	$ 0.06	$ 0.40					$ 1.82	$ 1.00	$ 0.92
Basic earnings per share (in dollars per share)					$ 0.35	$ 0.13	$ 0.09	$ 0.43
Diluted earnings per share (in dollars per share)					0.35	0.13	0.09	0.42
Dividends declared (in dollars per share)	$ 0.21	$ 0.21	$ 0.21	$ 0.21	$ 0.21	$ 0.21	$ 0.21	$ 0.21