Guarantor and Non-Guarantor Financial Information (Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Condensed Financial Statements, Captions [Line Items]
Net income applicable to Piedmont	$ 8,422	$ 8,153	$ 50,208	$ 16,114	$ 10,942	$ 57,830	$ 66,783	$ 84,886
Effective portion of gain/(loss) on derivative instruments that are designated and qualify as cash flow hedges (See Note 5)	(1,386)			1,144			(6,874)	4,408
Plus: Reclassification of gain included in net income	(427)			(434)			(1,871)	373
Other comprehensive income/(loss)	(1,813)	$ (4,137)	$ (2,795)	710	$ 1,502	$ 2,569	(8,745)	4,781
Comprehensive income applicable to Piedmont	6,609			16,824			58,038	89,667
Reportable Legal Entities | Piedmont (Parent) (Guarantor)
Condensed Financial Statements, Captions [Line Items]
Net income applicable to Piedmont	8,422			16,114			66,783	84,886
Effective portion of gain/(loss) on derivative instruments that are designated and qualify as cash flow hedges (See Note 5)	(1,386)			1,144			(6,874)	4,408
Plus: Reclassification of gain included in net income	(427)			(434)			(1,871)	373
Other comprehensive income/(loss)	(1,813)			710			(8,745)	4,781
Comprehensive income applicable to Piedmont	6,609			16,824			58,038	89,667
Reportable Legal Entities | Piedmont OP (the Issuer)
Condensed Financial Statements, Captions [Line Items]
Net income applicable to Piedmont	9,894			13,945			34,071	83,193
Effective portion of gain/(loss) on derivative instruments that are designated and qualify as cash flow hedges (See Note 5)	(1,386)			1,144			(6,874)	4,408
Plus: Reclassification of gain included in net income	(427)			(434)			(1,871)	373
Other comprehensive income/(loss)	(1,813)			710			(8,745)	4,781
Comprehensive income applicable to Piedmont	8,081			14,655			25,326	87,974
Reportable Legal Entities | Non-Guarantors
Condensed Financial Statements, Captions [Line Items]
Net income applicable to Piedmont	21,463			28,998			104,925	120,934
Effective portion of gain/(loss) on derivative instruments that are designated and qualify as cash flow hedges (See Note 5)	0			0			0	0
Plus: Reclassification of gain included in net income	0			0			0	0
Other comprehensive income/(loss)	0			0			0	0
Comprehensive income applicable to Piedmont	21,463			28,998			104,925	120,934
Eliminations
Condensed Financial Statements, Captions [Line Items]
Net income applicable to Piedmont	(31,357)			(42,943)			(138,996)	(204,127)
Effective portion of gain/(loss) on derivative instruments that are designated and qualify as cash flow hedges (See Note 5)	1,386			(1,144)			6,874	(4,408)
Plus: Reclassification of gain included in net income	427			434			1,871	(373)
Other comprehensive income/(loss)	1,813			(710)			8,745	(4,781)
Comprehensive income applicable to Piedmont	$ (29,544)			$ (43,653)			$ (130,251)	$ (208,908)