Quarterly Results (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Statement of Income Data:
Revenues	$ 143,911	$ 138,485	$ 135,307	$ 138,012	$ 139,461	$ 148,815	$ 146,734	$ 149,759	$ 146,711	$ 144,641	$ 138,580	$ 136,320	$ 555,715		$ 584,769		$ 566,252
Impairment loss on real estate assets	0	22,951	10,950	0	0	37,105	6,196	0					33,901	[1]	43,301	[1]	0	[1]
Real estate operating income	26,633	2,988	14,791	26,372	28,938	(3,424)	19,983	28,214	28,789	27,199	26,556	25,277	70,784		73,711		107,821
Income/(loss) from continuing operations	10,529	(13,065)	(1,553)	10,396	11,164	(21,318)	2,531	9,176	12,567	9,150	9,325	9,037	6,307		1,553		40,079
Income/(loss) from discontinued operations	0	1	(1)	0	72	14	(3)	0	(42)	16	882	360	0		83		1,216
Gain/(loss) on sale of real estate assets	19,652	(57)	73,835	(20)	84,427	14,796	21,520	8,940	(8)	0	878	0	93,410		129,683		870
Net income	30,181	(13,121)	72,281	10,376	95,663	(6,508)	24,048	18,116	12,517	9,166	11,085	9,397	99,717		131,319		42,165
Net income applicable to Piedmont	$ 30,189	$ (13,107)	$ 72,278	$ 10,372	$ 95,660	$ (6,512)	$ 24,044	$ 18,112	$ 12,514	$ 9,162	$ 11,081	$ 9,393	$ 99,732		$ 131,304		$ 42,150
Per share information— basic and diluted:
Net income/(loss) applicable to Piedmont	$ 0.21	$ (0.09)	$ 0.50	$ 0.07	$ 0.65	$ (0.05)	$ 0.15	$ 0.12	$ 0.08	$ 0.06	$ 0.07	$ 0.06	$ 0.69		$ 0.87		$ 0.27
Dividends declared per share	$ 0.21	$ 0.21	$ 0.21	$ 0.21	$ 0.21	$ 0.21	$ 0.21	$ 0.21	$ 0.21	$ 0.2	$ 0.2	$ 0.2
Balance Sheet Data:
Goodwill	$ 98,918	$ 98,918	$ 99,278	$ 104,786	$ 104,786	$ 134,770	$ 139,407	$ 145,340					$ 98,918		$ 104,786
Other assets held for sale, net	0	0	8,761	11,236	10,777	10,038	9,938	9,703					0		10,777
Total assets	4,368,168	4,307,118	4,217,680	4,281,993	4,361,511	4,689,613	4,735,408	4,780,000					4,368,168		4,361,511
Debt, net	2,020,475	1,994,078	1,884,314	2,002,918	2,029,510	2,421,099	2,312,804	2,318,717					2,020,475		2,029,510
Cumulative distributions in excess of earnings	(1,580,863)	(1,580,553)	(1,536,948)	(1,578,728)	(1,550,698)	(1,613,418)	(1,465,715)	(1,411,258)					(1,580,863)		(1,550,698)
Piedmont stockholders' equity	2,095,821	2,085,906	2,124,870	2,085,610	2,122,395	2,048,669	2,216,423	2,252,423					2,095,821		2,122,395
Total stockholders' equity	2,097,703	2,087,804	2,125,895	2,086,639	2,123,420	2,049,698	2,217,448	2,253,452	$ 2,280,677				2,097,703		2,123,420		$ 2,280,677		$ 2,431,019
Total liabilities and stockholders' equity	$ 4,368,168	$ 4,307,118	$ 4,217,680	$ 4,281,993	$ 4,361,511	$ 4,689,613	$ 4,735,408	$ 4,780,000					$ 4,368,168		$ 4,361,511

[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.