Guarantor and Non-Guarantor Financial Information (Income) (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended		12 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	Dec. 31, 2017
Revenues:
Rental and tenant reimbursement revenue	$ 130,579		$ 504,400	$ 124,518			$ 382,213	$ 372,491	$ 553,300
Total revenues	135,421			129,708			399,025	388,782
Expenses:
Property operating costs	54,613			49,679			158,798	154,175
Depreciation	27,131			26,852			80,004	81,112
Amortization	19,505			14,840			55,666	46,818
Impairment loss on real estate assets	1,953			0			1,953	0
General and administrative	7,950			6,677			29,736	21,487
Operating expenses	111,152			98,048			326,157	303,592
Other income (expense):
Interest expense	(16,145)			(15,849)			(46,750)	(45,294)
Other income/(expense)	263			303			1,292	1,480
Loss on extinguishment of debt	0			0			0	(1,680)
Gain on sale of real estate assets	32			0			39,370	45,186
Nonoperating income (expense	(15,850)			(15,546)			(6,088)	(308)
Income/(loss) before consolidated subsidiaries	8,419			16,114			66,780	84,882
Income from subsidiaries	0			0			0	0
Net income	8,419			16,114			66,780	84,882
Net loss applicable to noncontrolling interest	3	$ 1	(1)	0	$ 2	$ 2	3	4
Net income applicable to Piedmont	8,422	$ 8,153	$ 50,208	16,114	$ 10,942	$ 57,830	66,783	84,886
Eliminations
Revenues:
Rental and tenant reimbursement revenue	(746)			(694)			(2,150)	(1,802)
Total revenues	(4,963)			(4,622)			(14,292)	(13,368)
Expenses:
Property operating costs	(4,963)			(4,622)			(14,292)	(13,368)
Depreciation	0			0			0	0
Amortization	0			0			0	0
Impairment loss on real estate assets	0						0
General and administrative	0			0			0	0
Operating expenses	(4,963)			(4,622)			(14,292)	(13,368)
Other income (expense):
Interest expense	1,894			1,894			5,641	5,736
Other income/(expense)	(1,894)			(1,894)			(5,641)	(5,736)
Loss on extinguishment of debt								0
Gain on sale of real estate assets	0						0	0
Nonoperating income (expense				0			0	0
Income/(loss) before consolidated subsidiaries	0			0			0	0
Income from subsidiaries	(31,357)			(42,943)			(138,996)	(204,127)
Net income	(31,357)			(42,943)			(138,996)	(204,127)
Net loss applicable to noncontrolling interest	0			0			0	0
Net income applicable to Piedmont	(31,357)			(42,943)			(138,996)	(204,127)
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	36			0			36	0
Depreciation	0			0			0	0
Amortization	0			0			0	0
Impairment loss on real estate assets	0						0
General and administrative	(30)			42			165	228
Operating expenses	6			42			201	228
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
Nonoperating income (expense				0			0	0
Income/(loss) before consolidated subsidiaries	(6)			(42)			(201)	(228)
Income from subsidiaries	8,428			16,156			66,984	85,114
Net income	8,422			16,114			66,783	84,886
Net loss applicable to noncontrolling interest	0			0			0	0
Net income applicable to Piedmont	8,422			16,114			66,783	84,886
Piedmont OP (the Issuer) | Reportable Legal Entities
Revenues:
Rental and tenant reimbursement revenue	11,940			10,861			34,477	33,754
Total revenues	11,980			10,896			34,594	33,846
Expenses:
Property operating costs	5,507			4,973			15,848	14,614
Depreciation	3,062			2,816			9,041	8,527
Amortization	486			446			1,435	1,520
Impairment loss on real estate assets	0						0
General and administrative	1,547			1,424			4,874	4,849
Operating expenses	10,602			9,659			31,198	29,510
Other income (expense):
Interest expense	(14,429)			(14,119)			(41,590)	(40,093)
Other income/(expense)	16			40			125	200
Loss on extinguishment of debt								(1,680)
Gain on sale of real estate assets	0						128	1,417
Nonoperating income (expense				(14,079)			(41,337)	(40,156)
Income/(loss) before consolidated subsidiaries	(13,035)			(12,842)			(37,941)	(35,820)
Income from subsidiaries	22,929			26,787			72,012	119,013
Net income	9,894			13,945			34,071	83,193
Net loss applicable to noncontrolling interest	0			0			0	0
Net income applicable to Piedmont	9,894			13,945			34,071	83,193
Non-Guarantors | Reportable Legal Entities
Revenues:
Rental and tenant reimbursement revenue	119,385			114,351			349,886	340,539
Total revenues	128,404			123,434			378,723	368,304
Expenses:
Property operating costs	54,033			49,328			157,206	152,929
Depreciation	24,069			24,036			70,963	72,585
Amortization	19,019			14,394			54,231	45,298
Impairment loss on real estate assets	1,953						1,953
General and administrative	6,433			5,211			24,697	16,410
Operating expenses	105,507			92,969			309,050	287,222
Other income (expense):
Interest expense	(3,610)			(3,624)			(10,801)	(10,937)
Other income/(expense)	2,141			2,157			6,808	7,016
Loss on extinguishment of debt								0
Gain on sale of real estate assets	32						39,242	43,769
Nonoperating income (expense				(1,467)			35,249	39,848
Income/(loss) before consolidated subsidiaries	21,460			28,998			104,922	120,930
Income from subsidiaries	0			0			0	0
Net income	21,460			28,998			104,922	120,930
Net loss applicable to noncontrolling interest	3			0			3	4
Net income applicable to Piedmont	21,463			28,998			104,925	120,934
Property management fee revenue
Revenues:
Property management and other property related revenue	405			368			2,819	1,059
Property management fee revenue | Eliminations
Revenues:
Property management and other property related revenue	(4,217)			(3,928)			(12,142)	(11,566)
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	4,622			4,296			14,961	12,625
Other property related income
Revenues:
Property management and other property related revenue	4,437			4,822			13,993	15,232
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			35			117	92
Other property related income | Non-Guarantors | Reportable Legal Entities
Revenues:
Property management and other property related revenue	$ 4,397			$ 4,787			$ 13,876	$ 15,140