Quarterly Results (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
	Dec. 13, 2017	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Revenues		$ 137,185	$ 129,708	$ 129,174	$ 129,900	$ 139,444	$ 137,587	$ 148,679	$ 148,463	$ 525,967	$ 574,173	$ 555,715
Gain/(loss) on sale of real estate assets		30,505	0	(23)	45,209	(77)	109,512	6,492	(53)	75,691	115,874	93,410
Net income		45,409	16,114	10,940	57,828	(31,388)	126,129	23,707	15,101	130,291	133,549	99,717
Net income/(loss) applicable to Piedmont		$ 45,410	$ 16,114	$ 10,942	$ 57,830	$ (31,383)	$ 126,133	$ 23,710	$ 15,104	$ 130,296	$ 133,564	$ 99,732
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
Basic and diluted earnings/(loss) per share (in dollars per share)						$ (0.21)	$ 0.87	$ 0.16	$ 0.10	$ 1.00	$ 0.92	$ 0.69
Dividends declared (in dollars per share)		$ 0.21	$ 0.21	$ 0.21	$ 0.21	$ 0.71	$ 0.21	$ 0.21	$ 0.21
Special dividend (in dollars per share)	$ 0.50									$ 0.84	$ 1.34	$ 0.84