Guarantor and Non-Guarantor Financial Information - Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Real estate assets, at cost:
Land	$ 507,422	$ 490,625
Buildings and improvements, less accumulated depreciation	2,305,096	2,243,519
Intangible lease assets, less accumulated amortization	77,676	77,805
Construction in progress	15,848	11,344
Real estate assets held for sale, net	110,552	561,449
Total real estate assets	3,016,594	3,384,742
Cash and cash equivalents	4,571	7,382	$ 6,992	$ 5,441
Tenant and straight-line receivables, net	173,389	156,618
Advances to affiliates		0
Investment in subsidiaries	0	0
Notes receivable	0	0
Prepaid expenses, restricted cash, escrows, interest rate swaps, and other assets	28,018	22,839
Goodwill	98,918	98,918
Deferred lease costs, net	250,148	245,175
Other assets held for sale, net	20,791	84,293
Total assets	3,592,429	3,999,967
Liabilities:
Debt, net	1,686,311	1,726,927
Accounts payable, accrued expenses, dividends payable, interest rate swaps and accrued capital expenditures	129,491	216,653
Advances from affiliates		0
Deferred income	28,779	29,582
Intangible lease liabilities, net	35,708	38,458
Interest rate swaps	839	1,478
Liabilities held for sale, net	0	380
Total liabilities	1,880,289	2,013,478
Equity:
Total stockholders’ equity	1,712,140	1,986,489	$ 2,097,703	$ 2,123,420
Total liabilities and stockholders’ equity	3,592,429	3,999,967
Eliminations
Real estate assets, at cost:
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	0
Total real estate assets	(300)	(300)
Cash and cash equivalents	(518)	0
Tenant and straight-line receivables, net	0	0
Advances to affiliates		(7,971,908)
Investment in subsidiaries	(4,448,625)	(3,437,471)
Notes receivable	(145,310)	(233,310)
Prepaid expenses, restricted cash, escrows, interest rate swaps, and other assets	(24)	(740)
Goodwill	0	0
Deferred lease costs, net	0	0
Other assets held for sale, net	0	0
Total assets	(4,594,777)	(11,643,729)
Liabilities:
Debt, net	(145,310)	(233,310)
Accounts payable, accrued expenses, dividends payable, interest rate swaps and accrued capital expenditures	(542)	(740)
Advances from affiliates		(8,070,163)
Deferred income	0	0
Intangible lease liabilities, net	0	0
Interest rate swaps		0
Liabilities held for sale, net		0
Total liabilities	(145,852)	(8,304,213)
Equity:
Total stockholders’ equity	(4,448,925)	(3,339,516)
Total liabilities and stockholders’ equity	(4,594,777)	(11,643,729)
Piedmont (Parent) (Guarantor) | Reportable Legal Entities
Real estate assets, at cost:
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	0
Total real estate assets	0	0
Cash and cash equivalents	150	150
Tenant and straight-line receivables, net	0	0
Advances to affiliates		1,674,276
Investment in subsidiaries	1,744,122	3,437,299
Notes receivable	0	0
Prepaid expenses, restricted cash, escrows, interest rate swaps, and other assets	42	2
Goodwill	0	0
Deferred lease costs, net	0	0
Other assets held for sale, net	0	0
Total assets	1,744,314	5,111,727
Liabilities:
Debt, net	0	0
Accounts payable, accrued expenses, dividends payable, interest rate swaps and accrued capital expenditures	32,174	104,028
Advances from affiliates		5,277,957
Deferred income	0	0
Intangible lease liabilities, net	0	0
Interest rate swaps		0
Liabilities held for sale, net		0
Total liabilities	32,174	5,381,985
Equity:
Total stockholders’ equity	1,712,140	(270,258)
Total liabilities and stockholders’ equity	1,744,314	5,111,727
Piedmont OP (the Issuer) | Reportable Legal Entities
Real estate assets, at cost:
Land	36,094	36,094
Buildings and improvements, less accumulated depreciation	176,927	180,886
Intangible lease assets, less accumulated amortization	0	181
Construction in progress	5,708	85
Real estate assets held for sale, net	0	32,815
Total real estate assets	218,729	250,061
Cash and cash equivalents	0	3,890
Tenant and straight-line receivables, net	16,143	16,891
Advances to affiliates		6,297,632
Investment in subsidiaries	2,704,337	0
Notes receivable	810	88,810
Prepaid expenses, restricted cash, escrows, interest rate swaps, and other assets	5,682	5,094
Goodwill	98,918	98,918
Deferred lease costs, net	15,158	16,611
Other assets held for sale, net	0	2,266
Total assets	3,059,777	6,780,173
Liabilities:
Debt, net	1,495,904	1,535,239
Accounts payable, accrued expenses, dividends payable, interest rate swaps and accrued capital expenditures	14,543	20,279
Advances from affiliates		941,494
Deferred income	2,274	3,631
Intangible lease liabilities, net	0	0
Interest rate swaps		1,478
Liabilities held for sale, net		0
Total liabilities	1,512,721	2,502,121
Equity:
Total stockholders’ equity	1,547,056	4,278,052
Total liabilities and stockholders’ equity	3,059,777	6,780,173
Non-Guarantor Subsidiaries | Reportable Legal Entities
Real estate assets, at cost:
Land	471,328	454,531
Buildings and improvements, less accumulated depreciation	2,128,469	2,062,933
Intangible lease assets, less accumulated amortization	77,676	77,624
Construction in progress	10,140	11,259
Real estate assets held for sale, net	110,552	528,634
Total real estate assets	2,798,165	3,134,981
Cash and cash equivalents	4,939	3,342
Tenant and straight-line receivables, net	157,246	139,727
Advances to affiliates		0
Investment in subsidiaries	166	172
Notes receivable	144,500	144,500
Prepaid expenses, restricted cash, escrows, interest rate swaps, and other assets	22,318	18,483
Goodwill	0	0
Deferred lease costs, net	234,990	228,564
Other assets held for sale, net	20,791	82,027
Total assets	3,383,115	3,751,796
Liabilities:
Debt, net	335,717	424,998
Accounts payable, accrued expenses, dividends payable, interest rate swaps and accrued capital expenditures	83,316	93,086
Advances from affiliates		1,850,712
Deferred income	26,505	25,951
Intangible lease liabilities, net	35,708	38,458
Interest rate swaps		0
Liabilities held for sale, net		380
Total liabilities	481,246	2,433,585
Equity:
Total stockholders’ equity	2,901,869	1,318,211
Total liabilities and stockholders’ equity	$ 3,383,115	$ 3,751,796