Guarantor and Non-Guarantor Financial Information (Income) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Revenues:
Rental and tenant reimbursement revenue	$ 125,468		$ 123,525		$ 251,634	$ 247,973	$ 504,400	$ 553,300
Total revenues	130,668		129,174		263,604	259,074
Expenses:
Property operating costs	52,380		52,637		104,185	104,496
Depreciation	26,348		27,115		52,873	54,260
Amortization	18,461		15,245		36,161	31,978
General and administrative	12,418		8,258		21,786	14,810
Operating expenses	109,607		103,255		215,005	205,544
Other income (expense):
Interest expense	(15,112)		(15,687)		(30,605)	(29,445)
Other income/(expense)	752		731		1,029	1,177
Loss on extinguishment of debt	0		0		0	(1,680)
Gain on sale of real estate assets	1,451		(23)		39,338	45,186
Nonoperating Income (Expense)			(14,979)		9,762	15,238
Income/(loss) before consolidated subsidiaries	8,152		10,940		58,361	68,768
Income from subsidiaries	0		0		0	0
Net income	8,152		10,940		58,361	68,768
Net loss applicable to noncontrolling interest	1	$ (1)	2	$ (2)	0	4
Net income applicable to Piedmont	8,153	$ 50,208	10,942	$ 57,830	58,361	68,772
Eliminations
Revenues:
Rental and tenant reimbursement revenue	(709)		(592)		(1,404)	(1,108)
Total revenues	(4,618)		(4,357)		(9,329)	(8,745)
Expenses:
Property operating costs	(4,618)		(4,357)		(9,329)	(8,745)
Depreciation	0		0		0	0
Amortization	0		0		0	0
General and administrative	0		0		0	0
Operating expenses	(4,618)		(4,357)		(9,329)	(8,745)
Other income (expense):
Interest expense	1,880		1,880		3,747	3,842
Other income/(expense)	(1,880)		(1,880)		(3,747)	(3,842)
Loss on extinguishment of debt						0
Gain on sale of real estate assets	0		0		0	0
Nonoperating Income (Expense)			0		0	0
Income/(loss) before consolidated subsidiaries	0		0		0	0
Income from subsidiaries	(32,365)		(35,585)		(107,639)	(161,184)
Net income	(32,365)		(35,585)		(107,639)	(161,184)
Net loss applicable to noncontrolling interest	0		0		0	0
Net income applicable to Piedmont	(32,365)		(35,585)		(107,639)	(161,184)
Piedmont (Parent) (Guarantor) | Reportable Legal Entities
Revenues:
Rental and tenant reimbursement revenue	0		0		0	0
Total revenues	0		0		0	0
Expenses:
Property operating costs	0		0		0	0
Depreciation	0		0		0	0
Amortization	0		0		0	0
General and administrative	94		86		195	186
Operating expenses	94		86		195	186
Other income (expense):
Interest expense	0		0		0	0
Other income/(expense)	0		0		0	0
Loss on extinguishment of debt						0
Gain on sale of real estate assets	0		0		0	0
Nonoperating Income (Expense)			0		0	0
Income/(loss) before consolidated subsidiaries	(94)		(86)		(195)	(186)
Income from subsidiaries	8,247		11,028		58,556	68,958
Net income	8,153		10,942		58,361	68,772
Net loss applicable to noncontrolling interest	0		0		0	0
Net income applicable to Piedmont	8,153		10,942		58,361	68,772
Piedmont OP (the Issuer) | Reportable Legal Entities
Revenues:
Rental and tenant reimbursement revenue	11,271		11,433		22,536	22,892
Total revenues	11,311		11,462		22,613	22,949
Expenses:
Property operating costs	5,255		4,927		10,341	9,641
Depreciation	3,009		2,846		5,979	5,710
Amortization	469		463		949	1,074
General and administrative	1,567		1,539		3,327	3,425
Operating expenses	10,300		9,775		20,596	19,850
Other income (expense):
Interest expense	(13,392)		(13,953)		(27,162)	(25,975)
Other income/(expense)	38		36		110	160
Loss on extinguishment of debt						(1,680)
Gain on sale of real estate assets	0		(13)		128	1,417
Nonoperating Income (Expense)			(13,930)		(26,924)	(26,078)
Income/(loss) before consolidated subsidiaries	(12,343)		(12,243)		(24,907)	(22,979)
Income from subsidiaries	24,118		24,557		49,083	92,226
Net income	11,775		12,314		24,176	69,247
Net loss applicable to noncontrolling interest	0		0		0	0
Net income applicable to Piedmont	11,775		12,314		24,176	69,247
Non-Guarantors | Reportable Legal Entities
Revenues:
Rental and tenant reimbursement revenue	114,906		112,684		230,502	226,189
Total revenues	123,975		122,069		250,320	244,870
Expenses:
Property operating costs	51,743		52,067		103,173	103,600
Depreciation	23,339		24,269		46,894	48,550
Amortization	17,992		14,782		35,212	30,904
General and administrative	10,757		6,633		18,264	11,199
Operating expenses	103,831		97,751		203,543	194,253
Other income (expense):
Interest expense	(3,600)		(3,614)		(7,190)	(7,312)
Other income/(expense)	2,594		2,575		4,666	4,859
Loss on extinguishment of debt						0
Gain on sale of real estate assets	1,451		(10)		39,210	43,769
Nonoperating Income (Expense)			(1,049)		36,686	41,316
Income/(loss) before consolidated subsidiaries	20,589		23,269		83,463	91,933
Income from subsidiaries	0		0		0	0
Net income	20,589		23,269		83,463	91,933
Net loss applicable to noncontrolling interest	1		2		0	4
Net income applicable to Piedmont	20,590		23,271		83,463	91,937
Property management fee revenue
Revenues:
Property management and other property related revenue	422		382		2,414	691
Property management fee revenue | Eliminations
Revenues:
Property management and other property related revenue	(3,909)		(3,765)		(7,925)	(7,637)
Property management fee revenue | Piedmont (Parent) (Guarantor) | Reportable Legal Entities
Revenues:
Property management and other property related revenue	0		0		0	0
Property management fee revenue | Piedmont OP (the Issuer) | Reportable Legal Entities
Revenues:
Property management and other property related revenue	0		0		0	0
Property management fee revenue | Non-Guarantors | Reportable Legal Entities
Revenues:
Property management and other property related revenue	4,331		4,147		10,339	8,328
Other property related income
Revenues:
Property management and other property related revenue	4,778		5,267		9,556	10,410
Other property related income | Eliminations
Revenues:
Property management and other property related revenue	0		0		0	0
Other property related income | Piedmont (Parent) (Guarantor) | Reportable Legal Entities
Revenues:
Property management and other property related revenue	0		0		0	0
Other property related income | Piedmont OP (the Issuer) | Reportable Legal Entities
Revenues:
Property management and other property related revenue	40		29		77	57
Other property related income | Non-Guarantors | Reportable Legal Entities
Revenues:
Property management and other property related revenue	$ 4,738		$ 5,238		$ 9,479	$ 10,353