Guarantor and Non-Guarantor Financial Information (Balance Sheets) (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
Assets:
Land	$ 517,479		$ 507,422
Buildings and improvements, less accumulated depreciation	2,342,028		2,305,096
Intangible lease assets, less accumulated amortization	79,331		77,676
Construction in progress	13,252		15,848
Real estate assets held for sale, net	0		110,552
Total real estate assets	2,952,090		3,016,594
Cash and cash equivalents	7,748		4,571	$ 8,944		$ 7,382
Tenant and straight-line rent receivables	181,916		173,389
Investment in subsidiaries	0		0
Notes receivable	0		0
Prepaid expenses, restricted cash, escrows, interest rate swaps, and other assets	34,576		28,018
Goodwill	98,918		98,918
Deferred lease costs, net	250,119		250,148
Other assets held for sale, net	0		20,791
Total assets	3,525,367		3,592,429
Liabilities:
Debt, net	1,661,976		1,685,472
Accounts payable, accrued expenses, interest rate swaps and accrued capital expenditures	97,502		130,330
Deferred income	24,641		28,779
Intangible lease liabilities, net	32,724		35,708
Interest rate swaps	5,549		839
Total liabilities	1,822,392		1,880,289
Equity:
Total stockholders’ equity	1,702,975	$ 1,723,522	1,712,140	$ 1,743,056	$ 1,789,588	$ 1,986,489
Total liabilities and stockholders’ equity	3,525,367		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	(4,543,269)		(4,448,625)
Notes receivable	(145,310)		(145,310)
Prepaid expenses, restricted cash, escrows, interest rate swaps, and other assets	(52)		(24)
Goodwill	0		0
Deferred lease costs, net	0		0
Other assets held for sale, net			0
Total assets	(4,688,931)		(4,594,777)
Liabilities:
Debt, net	(145,310)		(145,310)
Accounts payable, accrued expenses, interest rate swaps and accrued capital expenditures	(52)		(542)
Deferred income	0		0
Intangible lease liabilities, net	0		0
Interest rate swaps	0
Total liabilities	(145,362)		(145,852)
Equity:
Total stockholders’ equity	(4,543,569)		(4,448,925)
Total liabilities and stockholders’ equity	(4,688,931)		(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	1,703,277		1,744,122
Notes receivable	0		0
Prepaid expenses, restricted cash, escrows, interest rate swaps, and other assets	71		42
Goodwill	0		0
Deferred lease costs, net	0		0
Other assets held for sale, net			0
Total assets	1,703,498		1,744,314
Liabilities:
Debt, net	0		0
Accounts payable, accrued expenses, interest rate swaps and accrued capital expenditures	523		32,174
Deferred income	0		0
Intangible lease liabilities, net	0		0
Interest rate swaps	0
Total liabilities	523		32,174
Equity:
Total stockholders’ equity	1,702,975		1,712,140
Total liabilities and stockholders’ equity	1,703,498		1,744,314
Piedmont OP (the Issuer) | Reportable Legal Entities
Assets:
Land	36,094		36,094
Buildings and improvements, less accumulated depreciation	186,061		176,927
Intangible lease assets, less accumulated amortization	0		0
Construction in progress	785		5,708
Real estate assets held for sale, net			0
Total real estate assets	222,940		218,729
Cash and cash equivalents	3,484		0
Tenant and straight-line rent receivables	16,744		16,143
Investment in subsidiaries	2,839,828		2,704,337
Notes receivable	810		810
Prepaid expenses, restricted cash, escrows, interest rate swaps, and other assets	5,868		5,682
Goodwill	98,918		98,918
Deferred lease costs, net	14,369		15,158
Other assets held for sale, net			0
Total assets	3,202,961		3,059,777
Liabilities:
Debt, net	1,472,146		1,495,065
Accounts payable, accrued expenses, interest rate swaps and accrued capital expenditures	13,085		15,382
Deferred income	2,210		2,274
Intangible lease liabilities, net	0		0
Interest rate swaps	5,549
Total liabilities	1,492,990		1,512,721
Equity:
Total stockholders’ equity	1,709,971		1,547,056
Total liabilities and stockholders’ equity	3,202,961		3,059,777
Non-Guarantors | Reportable Legal Entities
Assets:
Land	481,385		471,328
Buildings and improvements, less accumulated depreciation	2,156,267		2,128,469
Intangible lease assets, less accumulated amortization	79,331		77,676
Construction in progress	12,467		10,140
Real estate assets held for sale, net			110,552
Total real estate assets	2,729,450		2,798,165
Cash and cash equivalents	4,114		4,939
Tenant and straight-line rent receivables	165,172		157,246
Investment in subsidiaries	164		166
Notes receivable	144,500		144,500
Prepaid expenses, restricted cash, escrows, interest rate swaps, and other assets	28,689		22,318
Goodwill	0		0
Deferred lease costs, net	235,750		234,990
Other assets held for sale, net			20,791
Total assets	3,307,839		3,383,115
Liabilities:
Debt, net	335,140		335,717
Accounts payable, accrued expenses, interest rate swaps and accrued capital expenditures	83,946		83,316
Deferred income	22,431		26,505
Intangible lease liabilities, net	32,724		35,708
Interest rate swaps	0
Total liabilities	474,241		481,246
Equity:
Total stockholders’ equity	2,833,598		2,901,869
Total liabilities and stockholders’ equity	$ 3,307,839		$ 3,383,115