Guarantor and Non-Guarantor Financial Information - Condensed Consolidated Balance Sheets (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Assets:
Land	$ 675,281	$ 627,351
Buildings and improvements, less accumulated depreciation	3,049,905	2,891,323
Intangible lease assets, less accumulated amortization	66,870	54,744
Construction in progress	61,162	20,373
Real estate assets held for sale, net	19,734	18,941
Total real estate assets	3,872,952	3,612,732
Investments in and amounts due from unconsolidated joint ventures	18,668	37,689
Cash and cash equivalents	15,972	12,957	20,763	139,690
Tenant and straight-line rent receivables, net	166,493	146,544
Advances to affiliates	0	0
Investment in subsidiary	0	0
Notes receivable	0	0
Prepaid expenses, restricted cash, escrows, and other assets	17,995	13,356
Goodwill	180,097	180,097
Interest rate swaps	19,192	1,075
Deferred financing costs, net	7,990	6,454
Deferred lease costs, net	275,234	243,178
Other assets held for sale, net	1,960	793
Total assets	4,576,553	4,254,875
Liabilities:
Secured and unsecured debt	1,823,175	1,416,525
Accounts payable, accrued expenses, and accrued capital expenditures	159,675	127,263
Advances from affiliates	0	0
Deferred income	26,575	21,552
Intangible lease liabilities, net	41,435	40,805
Interest rate swaps	5,010	8,235
Total liabilities	2,055,870	1,614,380
Stockholders’ Equity:
Common stock	1,613	1,676
Additional paid-in capital	3,668,424	3,667,051
Cumulative distributions in excess of earnings	(1,165,794)	(1,022,681)
Other comprehensive income/(loss)	14,827	(7,160)
Piedmont stockholders’ equity	2,519,070	2,638,886
Noncontrolling interest	1,613	1,609
Total stockholders’ equity	2,520,683	2,640,495		2,773,428
Total liabilities and stockholders’ equity	4,576,553	4,254,875
Issuer [Member]
Assets:
Land	88,054	91,782
Buildings and improvements, less accumulated depreciation	492,098	511,793
Intangible lease assets, less accumulated amortization	2,547	3,265
Construction in progress	2,546	1,056
Real estate assets held for sale, net	19,734	18,941
Total real estate assets	604,979	626,837
Investments in and amounts due from unconsolidated joint ventures	18,668	37,689
Cash and cash equivalents	12,096	62,371	59,784	166,920
Tenant and straight-line rent receivables, net	35,914	33,495
Advances to affiliates	5,110,420	4,623,173
Investment in subsidiary	0	0
Notes receivable	160,000	160,000
Prepaid expenses, restricted cash, escrows, and other assets	5,671	4,218
Goodwill	180,097	180,097
Interest rate swaps	19,192	1,075
Deferred financing costs, net	6,703	4,292
Deferred lease costs, net	36,293	31,357
Other assets held for sale, net	1,960	793
Total assets	6,191,993	5,765,397
Liabilities:
Secured and unsecured debt	859,540	452,890
Accounts payable, accrued expenses, and accrued capital expenditures	20,937	20,443
Advances from affiliates	306,636	274,159
Deferred income	8,533	5,991
Intangible lease liabilities, net	6	24
Interest rate swaps	5,010	8,235
Total liabilities	1,200,662	761,742
Stockholders’ Equity:
Common stock	0	0
Additional paid-in capital	4,035,964	4,068,844
Cumulative distributions in excess of earnings	940,540	941,971
Other comprehensive income/(loss)	14,827	(7,160)
Piedmont stockholders’ equity	4,991,331	5,003,655
Noncontrolling interest	0	0
Total stockholders’ equity	4,991,331	5,003,655
Total liabilities and stockholders’ equity	6,191,993	5,765,397
Guarantor [Member]
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	0
Total real estate assets	0	0
Investments in and amounts due from unconsolidated joint ventures	0	0
Cash and cash equivalents	146	238	150	139
Tenant and straight-line rent receivables, net	0	0
Advances to affiliates	1,293,461	1,300,158
Investment in subsidiary	4,035,964	4,068,844
Notes receivable	2,000	2,500
Prepaid expenses, restricted cash, escrows, and other assets	47	15
Goodwill	0	0
Interest rate swaps	0	0
Deferred financing costs, net	0	0
Deferred lease costs, net	0	0
Other assets held for sale, net	0	0
Total assets	5,331,618	5,371,755
Liabilities:
Secured and unsecured debt	0	0
Accounts payable, accrued expenses, and accrued capital expenditures	1,360	645
Advances from affiliates	4,807,113	4,636,936
Deferred income	0	0
Intangible lease liabilities, net	0	0
Interest rate swaps	0	0
Total liabilities	4,808,473	4,637,581
Stockholders’ Equity:
Common stock	1,613	1,676
Additional paid-in capital	3,668,424	3,667,051
Cumulative distributions in excess of earnings	(3,146,892)	(2,934,553)
Other comprehensive income/(loss)	0	0
Piedmont stockholders’ equity	523,145	734,174
Noncontrolling interest	0	0
Total stockholders’ equity	523,145	734,174
Total liabilities and stockholders’ equity	5,331,618	5,371,755
Non-Guarantor Subsidiaries [Member]
Assets:
Land	587,227	535,569
Buildings and improvements, less accumulated depreciation	2,558,107	2,379,530
Intangible lease assets, less accumulated amortization	64,323	51,479
Construction in progress	58,616	19,317
Real estate assets held for sale, net	0	0
Total real estate assets	3,268,273	2,985,895
Investments in and amounts due from unconsolidated joint ventures	0	0
Cash and cash equivalents	3,730	(49,652)	(39,171)	(27,369)
Tenant and straight-line rent receivables, net	130,579	113,049
Advances to affiliates	(1,086,177)	(908,506)
Investment in subsidiary	199	200
Notes receivable	23,890	23,890
Prepaid expenses, restricted cash, escrows, and other assets	13,218	10,071
Goodwill	0	0
Interest rate swaps	0	0
Deferred financing costs, net	1,287	2,162
Deferred lease costs, net	238,941	211,821
Other assets held for sale, net	0	0
Total assets	2,593,940	2,388,930
Liabilities:
Secured and unsecured debt	1,149,525	1,150,025
Accounts payable, accrued expenses, and accrued capital expenditures	138,319	107,123
Advances from affiliates	244,499	135,940
Deferred income	18,042	15,561
Intangible lease liabilities, net	41,429	40,781
Interest rate swaps	0	0
Total liabilities	1,591,814	1,449,430
Stockholders’ Equity:
Common stock	0	0
Additional paid-in capital	199	200
Cumulative distributions in excess of earnings	1,000,314	937,691
Other comprehensive income/(loss)	0	0
Piedmont stockholders’ equity	1,000,513	937,891
Noncontrolling interest	1,613	1,609
Total stockholders’ equity	1,002,126	939,500
Total liabilities and stockholders’ equity	2,593,940	2,388,930
Eliminations [Member]
Assets:
Land	0	0
Buildings and improvements, less accumulated depreciation	(300)	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	(300)	0
Investments in and amounts due from unconsolidated joint ventures	0	0
Cash and cash equivalents	0	0	0	0
Tenant and straight-line rent receivables, net	0	0
Advances to affiliates	(5,317,704)	(5,014,825)
Investment in subsidiary	(4,036,163)	(4,069,044)
Notes receivable	(185,890)	(186,390)
Prepaid expenses, restricted cash, escrows, and other assets	(941)	(948)
Goodwill	0	0
Interest rate swaps	0	0
Deferred financing costs, net	0	0
Deferred lease costs, net	0	0
Other assets held for sale, net	0	0
Total assets	(9,540,998)	(9,271,207)
Liabilities:
Secured and unsecured debt	(185,890)	(186,390)
Accounts payable, accrued expenses, and accrued capital expenditures	(941)	(948)
Advances from affiliates	(5,358,248)	(5,047,035)
Deferred income	0	0
Intangible lease liabilities, net	0
Interest rate swaps	0	0
Total liabilities	(5,545,079)	(5,234,373)
Stockholders’ Equity:
Common stock	0	0
Additional paid-in capital	(4,036,163)	(4,069,044)
Cumulative distributions in excess of earnings	40,244	32,210
Other comprehensive income/(loss)	0	0
Piedmont stockholders’ equity	(3,995,919)	(4,036,834)
Noncontrolling interest	0	0
Total stockholders’ equity	(3,995,919)	(4,036,834)
Total liabilities and stockholders’ equity	$ (9,540,998)	$ (9,271,207)