Guarantor and Non-Guarantor Financial Information (Condensed Consolidating Balance Sheets) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Assets:
Land	$ 507,369	$ 507,422
Buildings and improvements, less accumulated depreciation	2,293,629	2,305,096
Intangible lease assets, less accumulated amortization	71,274	77,676
Construction in progress	13,225	15,848
Real estate assets held for sale, net	0	110,552
Total real estate assets	2,885,497	3,016,594
Cash and cash equivalents	4,625	4,571	$ 6,729	$ 7,382
Tenant and straight-line rent receivables	179,039	173,389
Investment in subsidiaries	0	0
Notes receivable	0	0
Prepaid expenses, restricted cash, escrows, interest rate swaps, and other assets	25,516	28,018
Goodwill	98,918	98,918
Deferred lease costs, net	239,847	250,148
Other assets held for sale, net	0	20,791
Total assets	3,433,442	3,592,429
Liabilities:
Debt, net	1,565,755	1,686,311
Accounts payable, accrued expenses, interest rate swaps and accrued capital expenditures	81,309	129,491
Deferred income	27,053	28,779
Intangible lease liabilities, net	33,360	35,708
Interest rate swaps	2,443	839
Total liabilities	1,709,920	1,880,289
Equity:
Total stockholders’ equity	1,723,522	1,712,140	$ 1,789,588	$ 1,986,489
Total liabilities and stockholders’ equity	3,433,442	3,592,429
Eliminations
Assets:
Land	0	0
Buildings and improvements, less accumulated depreciation	(300)	(300)
Intangible lease assets, less accumulated amortization	0	0
Construction in progress	0	0
Real estate assets held for sale, net		0
Total real estate assets	(300)	(300)
Cash and cash equivalents	0	(518)
Tenant and straight-line rent receivables	0	0
Investment in subsidiaries	(4,416,309)	(4,448,625)
Notes receivable	(145,310)	(145,310)
Prepaid expenses, restricted cash, escrows, interest rate swaps, and other assets	(38)	(24)
Goodwill	0	0
Deferred lease costs, net	0	0
Other assets held for sale, net		0
Total assets	(4,561,957)	(4,594,777)
Liabilities:
Debt, net	(145,310)	(145,310)
Accounts payable, accrued expenses, interest rate swaps and accrued capital expenditures	(38)	(542)
Deferred income	0	0
Intangible lease liabilities, net	0	0
Interest rate swaps	0
Total liabilities	(145,348)	(145,852)
Equity:
Total stockholders’ equity	(4,416,609)	(4,448,925)
Total liabilities and stockholders’ equity	(4,561,957)	(4,594,777)
Piedmont (Parent) (Guarantor) | Reportable Legal Entities
Assets:
Land	0	0
Buildings and improvements, less accumulated depreciation	0	0
Intangible lease assets, less accumulated amortization	0	0
Construction in progress	0	0
Real estate assets held for sale, net		0
Total real estate assets	0	0
Cash and cash equivalents	150	150
Tenant and straight-line rent receivables	0	0
Investment in subsidiaries	1,724,045	1,744,122
Notes receivable	0	0
Prepaid expenses, restricted cash, escrows, interest rate swaps, and other assets	146	42
Goodwill	0	0
Deferred lease costs, net	0	0
Other assets held for sale, net		0
Total assets	1,724,341	1,744,314
Liabilities:
Debt, net	0	0
Accounts payable, accrued expenses, interest rate swaps and accrued capital expenditures	819	32,174
Deferred income	0	0
Intangible lease liabilities, net	0	0
Interest rate swaps	0
Total liabilities	819	32,174
Equity:
Total stockholders’ equity	1,723,522	1,712,140
Total liabilities and stockholders’ equity	1,724,341	1,744,314
Piedmont OP (the Issuer) | Reportable Legal Entities
Assets:
Land	36,094	36,094
Buildings and improvements, less accumulated depreciation	182,302	176,927
Intangible lease assets, less accumulated amortization	0	0
Construction in progress	251	5,708
Real estate assets held for sale, net		0
Total real estate assets	218,647	218,729
Cash and cash equivalents	1,411	0
Tenant and straight-line rent receivables	16,638	16,143
Investment in subsidiaries	2,692,100	2,704,337
Notes receivable	810	810
Prepaid expenses, restricted cash, escrows, interest rate swaps, and other assets	5,025	5,682
Goodwill	98,918	98,918
Deferred lease costs, net	14,913	15,158
Other assets held for sale, net		0
Total assets	3,048,462	3,059,777
Liabilities:
Debt, net	1,375,594	1,495,904
Accounts payable, accrued expenses, interest rate swaps and accrued capital expenditures	12,110	14,543
Deferred income	2,756	2,274
Intangible lease liabilities, net	0	0
Interest rate swaps	2,443
Total liabilities	1,392,903	1,512,721
Equity:
Total stockholders’ equity	1,655,559	1,547,056
Total liabilities and stockholders’ equity	3,048,462	3,059,777
Non-Guarantors | Reportable Legal Entities
Assets:
Land	471,275	471,328
Buildings and improvements, less accumulated depreciation	2,111,627	2,128,469
Intangible lease assets, less accumulated amortization	71,274	77,676
Construction in progress	12,974	10,140
Real estate assets held for sale, net		110,552
Total real estate assets	2,667,150	2,798,165
Cash and cash equivalents	3,064	4,939
Tenant and straight-line rent receivables	162,401	157,246
Investment in subsidiaries	164	166
Notes receivable	144,500	144,500
Prepaid expenses, restricted cash, escrows, interest rate swaps, and other assets	20,383	22,318
Goodwill	0	0
Deferred lease costs, net	224,934	234,990
Other assets held for sale, net		20,791
Total assets	3,222,596	3,383,115
Liabilities:
Debt, net	335,471	335,717
Accounts payable, accrued expenses, interest rate swaps and accrued capital expenditures	68,418	83,316
Deferred income	24,297	26,505
Intangible lease liabilities, net	33,360	35,708
Interest rate swaps	0
Total liabilities	461,546	481,246
Equity:
Total stockholders’ equity	2,761,050	2,901,869
Total liabilities and stockholders’ equity	$ 3,222,596	$ 3,383,115