Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Cumulative Distributions in Excess of Earnings	Other Comprehensive Income/(Loss)	Non- controlling Interest
Balance at Dec. 31, 2017	$ 1,986,489	$ 1,424	$ 3,677,360	$ (1,702,281)	$ 8,164	$ 1,822
Balance (in shares) at Dec. 31, 2017		142,359,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share repurchases as part of an announced plan	(231,888)	$ (125)		(231,763)
Share repurchases as part of an announced plan (in shares)		(12,482,000)
Dividends to common stockholders, stockholders of subsidiaries, and dividends reinvested	(28,311)		(19)	(28,284)		(8)
Shares issued and amortized under the 2007 Omnibus Incentive Plan, net of tax	2,901	$ 1	2,900
Shares issued and amortized under the 2007 Omnibus Incentive Plan, net of tax (in shares)		148,000
Net (income)/loss applicable to noncontrolling interest	(2)					(2)
Net income applicable to Piedmont	57,830			57,830
Other comprehensive loss	2,569				2,569
Balance at Mar. 31, 2018	1,789,588	$ 1,300	3,680,241	(1,904,404)	10,639	1,812
Balance (in shares) at Mar. 31, 2018		130,025,000
Balance at Dec. 31, 2017	1,986,489	$ 1,424	3,677,360	(1,702,281)	8,164	1,822
Balance (in shares) at Dec. 31, 2017		142,359,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (income)/loss applicable to noncontrolling interest	(4)
Net income applicable to Piedmont	84,886
Other comprehensive loss	4,781
Balance at Sep. 30, 2018	1,733,996	$ 1,284	3,682,209	(1,964,135)	12,851	1,787
Balance (in shares) at Sep. 30, 2018		128,371,000
Balance at Mar. 31, 2018	1,789,588	$ 1,300	3,680,241	(1,904,404)	10,639	1,812
Balance (in shares) at Mar. 31, 2018		130,025,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share repurchases as part of an announced plan	(32,897)	$ (18)	0	(32,879)
Share repurchases as part of an announced plan (in shares)		(1,861,000)
Dividends to common stockholders, stockholders of subsidiaries, and dividends reinvested	(26,997)		(32)	(26,950)		(15)
Shares issued and amortized under the 2007 Omnibus Incentive Plan, net of tax	920	$ 2	918
Shares issued and amortized under the 2007 Omnibus Incentive Plan, net of tax (in shares)		207,000
Net (income)/loss applicable to noncontrolling interest	(2)					(2)
Net income applicable to Piedmont	10,942			10,942
Other comprehensive loss	1,502				1,502
Balance at Jun. 30, 2018	1,743,056	$ 1,284	3,681,127	(1,953,291)	12,141	1,795
Balance (in shares) at Jun. 30, 2018		128,371,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders, stockholders of subsidiaries, and dividends reinvested	(26,971)		(5)	(26,958)		(8)
Shares issued and amortized under the 2007 Omnibus Incentive Plan, net of tax	1,087	$ 0	1,087
Shares issued and amortized under the 2007 Omnibus Incentive Plan, net of tax (in shares)		0
Net (income)/loss applicable to noncontrolling interest	0
Net income applicable to Piedmont	16,114			16,114
Other comprehensive loss	710				710
Balance at Sep. 30, 2018	1,733,996	$ 1,284	3,682,209	(1,964,135)	12,851	1,787
Balance (in shares) at Sep. 30, 2018		128,371,000
Balance at Dec. 31, 2018	$ 1,712,140	$ 1,262	3,683,186	(1,982,542)	8,462	1,772
Balance (in shares) at Dec. 31, 2018	126,218,554	126,219,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share repurchases as part of an announced plan	$ (12,482)	$ (7)		(12,475)
Share repurchases as part of an announced plan (in shares)		(728,000)
Dividends to common stockholders, stockholders of subsidiaries, and dividends reinvested	(26,430)		(48)	(26,375)		(7)
Shares issued and amortized under the 2007 Omnibus Incentive Plan, net of tax	2,880	$ 1	2,879
Shares issued and amortized under the 2007 Omnibus Incentive Plan, net of tax (in shares)		106,000
Net (income)/loss applicable to noncontrolling interest	1					1
Net income applicable to Piedmont	50,208			50,208
Other comprehensive loss	(2,795)				(2,795)
Balance at Mar. 31, 2019	1,723,522	$ 1,256	3,686,017	(1,971,184)	5,667	1,766
Balance (in shares) at Mar. 31, 2019		125,597,000
Balance at Dec. 31, 2018	$ 1,712,140	$ 1,262	3,683,186	(1,982,542)	8,462	1,772
Balance (in shares) at Dec. 31, 2018	126,218,554	126,219,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net (income)/loss applicable to noncontrolling interest	$ (3)
Net income applicable to Piedmont	66,783
Other comprehensive loss	(8,745)
Balance at Sep. 30, 2019	$ 1,680,783	$ 1,258	3,685,504	(2,007,438)	(283)	1,742
Balance (in shares) at Sep. 30, 2019	125,783,408	125,783,000
Balance at Mar. 31, 2019	$ 1,723,522	$ 1,256	3,686,017	(1,971,184)	5,667	1,766
Balance (in shares) at Mar. 31, 2019		125,597,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Dividends to common stockholders, stockholders of subsidiaries, and dividends reinvested	(26,522)		(94)	(26,415)		(13)
Shares issued and amortized under the 2007 Omnibus Incentive Plan, net of tax	1,960	$ 2	1,958
Shares issued and amortized under the 2007 Omnibus Incentive Plan, net of tax (in shares)		186,000
Net (income)/loss applicable to noncontrolling interest	(1)					(1)
Net income applicable to Piedmont	8,153			8,153
Other comprehensive loss	(4,137)				(4,137)
Balance at Jun. 30, 2019	1,702,975	$ 1,258	3,687,881	(1,989,446)	1,530	1,752
Balance (in shares) at Jun. 30, 2019		125,783,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Offering costs	(700)		(700)
Dividends to common stockholders, stockholders of subsidiaries, and dividends reinvested	(26,495)		(74)	(26,414)		(7)
Shares issued and amortized under the 2007 Omnibus Incentive Plan, net of tax	(1,603)	$ 0	(1,603)
Shares issued and amortized under the 2007 Omnibus Incentive Plan, net of tax (in shares)		0
Net (income)/loss applicable to noncontrolling interest	(3)					(3)
Net income applicable to Piedmont	8,422			8,422
Other comprehensive loss	(1,813)				(1,813)
Balance at Sep. 30, 2019	$ 1,680,783	$ 1,258	$ 3,685,504	$ (2,007,438)	$ (283)	$ 1,742
Balance (in shares) at Sep. 30, 2019	125,783,408	125,783,000