Guarantor and Non-Guarantor Financial Information - Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Assets:
Land	$ 696,713	$ 698,519
Buildings and improvements, less accumulated depreciation	3,154,044	3,196,660
Intangible lease assets, less accumulated amortization	64,152	70,177
Construction in progress	64,804	63,382
Total real estate assets held for sale, net	26,111	46,354
Total real estate assets	4,005,824	4,075,092
Investments in and amounts due from unconsolidated joint ventures	7,714	7,798
Cash and cash equivalents	8,997	12,306	$ 8,563	$ 6,973
Tenant and straight-line rent receivables, net	196,715	195,368
Advances to affiliates	0	0
Investment in subsidiary	0	0
Notes receivable	45,400	0
Notes receivable		0
Prepaid expenses, restricted cash, escrows, and other assets	33,312	33,499
Goodwill	180,097	180,097
Interest rate swaps	8,290	430
Deferred financing costs, net	7,491	7,667
Deferred lease costs, net	283,756	278,461
Other assets held for sale	3,706	4,783
Total assets	4,781,302	4,795,501
Liabilities:
Debt, net	2,320,295	2,277,589
Accounts payable, accrued expenses, and accrued capital expenditures	128,898	133,988
Advances from affiliates	0	0
Deferred income	26,633	22,215
Intangible lease liabilities, net	41,214	43,277
Interest rate swaps	8,411	6,417
Total liabilities	2,525,451	2,483,486
Stockholders’ Equity:
Common stock	1,518	1,543
Additional paid-in capital	3,668,378	3,666,182
Cumulative distributions in excess of earnings	(1,427,312)	(1,365,620)
Other comprehensive income	12,242	8,301
Piedmont stockholders’ equity	2,254,826	2,310,406
Noncontrolling interest	1,025	1,609
Total stockholders’ equity	2,255,851	2,312,015		2,461,159
Total liabilities and stockholders’ equity	4,781,302	4,795,501
Issuer [Member]
Assets:
Land	66,997	77,125
Buildings and improvements, less accumulated depreciation	355,127	414,515
Intangible lease assets, less accumulated amortization	1,541	1,812
Construction in progress	2,298	1,345
Total real estate assets held for sale, net	26,111	46,354
Total real estate assets	452,074	541,151
Investments in and amounts due from unconsolidated joint ventures	7,714	7,798
Cash and cash equivalents	6,164	8,143	5,330	3,261
Tenant and straight-line rent receivables, net	28,213	35,363
Advances to affiliates	6,337,046	6,084,243
Investment in subsidiary	0	0
Notes receivable	134,750
Notes receivable		161,350
Prepaid expenses, restricted cash, escrows, and other assets	6,214	10,912
Goodwill	180,097	180,097
Interest rate swaps	8,290	430
Deferred financing costs, net	6,699	7,242
Deferred lease costs, net	23,388	29,696
Other assets held for sale	3,706	4,783
Total assets	7,194,355	7,071,208
Liabilities:
Debt, net	1,841,428	1,852,434
Accounts payable, accrued expenses, and accrued capital expenditures	16,042	19,403
Advances from affiliates	558,055	376,122
Deferred income	4,069	4,998
Intangible lease liabilities, net	0	0
Interest rate swaps	8,411	6,417
Total liabilities	2,428,005	2,259,374
Stockholders’ Equity:
Common stock	0	0
Additional paid-in capital	3,810,131	3,874,757
Cumulative distributions in excess of earnings	943,977	928,776
Other comprehensive income	12,242	8,301
Piedmont stockholders’ equity	4,766,350	4,811,834
Noncontrolling interest	0	0
Total stockholders’ equity	4,766,350	4,811,834
Total liabilities and stockholders’ equity	7,194,355	7,071,208
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
Total 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	150	1,790	150	150
Tenant and straight-line rent receivables, net	0	0
Advances to affiliates	1,261,120	1,282,443
Investment in subsidiary	3,814,131	3,878,811
Notes receivable	0
Notes receivable		0
Prepaid expenses, restricted cash, escrows, and other assets	77	0
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	0	0
Total assets	5,075,478	5,163,044
Liabilities:
Debt, net	0	0
Accounts payable, accrued expenses, and accrued capital expenditures	6,783	465
Advances from affiliates	4,925,597	4,909,362
Deferred income	0	0
Intangible lease liabilities, net	0	0
Interest rate swaps	0	0
Total liabilities	4,932,380	4,909,827
Stockholders’ Equity:
Common stock	1,518	1,543
Additional paid-in capital	3,671,250	3,670,236
Cumulative distributions in excess of earnings	(3,529,670)	(3,418,562)
Other comprehensive income	0	0
Piedmont stockholders’ equity	143,098	253,217
Noncontrolling interest	0	0
Total stockholders’ equity	143,098	253,217
Total liabilities and stockholders’ equity	5,075,478	5,163,044
Non-Guarantor Subsidiaries [Member]
Assets:
Land	629,716	621,394
Buildings and improvements, less accumulated depreciation	2,799,217	2,782,445
Intangible lease assets, less accumulated amortization	62,611	68,365
Construction in progress	62,506	62,037
Total real estate assets held for sale, net	0	0
Total real estate assets	3,554,050	3,534,241
Investments in and amounts due from unconsolidated joint ventures	0	0
Cash and cash equivalents	2,683	2,373	3,083	3,562
Tenant and straight-line rent receivables, net	168,502	160,005
Advances to affiliates	0	0
Investment in subsidiary	189	192
Notes receivable	23,890
Notes receivable		23,890
Prepaid expenses, restricted cash, escrows, and other assets	28,520	23,541
Goodwill	0	0
Interest rate swaps	0	0
Deferred financing costs, net	792	425
Deferred lease costs, net	260,368	248,765
Other assets held for sale	0	0
Total assets	4,038,994	3,993,432
Liabilities:
Debt, net	592,107	610,395
Accounts payable, accrued expenses, and accrued capital expenditures	107,572	115,074
Advances from affiliates	2,180,736	2,138,140
Deferred income	22,564	17,217
Intangible lease liabilities, net	41,214	43,277
Interest rate swaps	0	0
Total liabilities	2,944,193	2,924,103
Stockholders’ Equity:
Common stock	0	0
Additional paid-in capital	1,317	192
Cumulative distributions in excess of earnings	1,092,459	1,067,528
Other comprehensive income	0	0
Piedmont stockholders’ equity	1,093,776	1,067,720
Noncontrolling interest	1,025	1,609
Total stockholders’ equity	1,094,801	1,069,329
Total liabilities and stockholders’ equity	4,038,994	3,993,432
Eliminations [Member]
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
Total real estate assets held for sale, net	0	0
Total real estate assets	(300)	(300)
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	(7,598,166)	(7,366,686)
Investment in subsidiary	(3,814,320)	(3,879,003)
Notes receivable	(113,240)
Notes receivable		(185,240)
Prepaid expenses, restricted cash, escrows, and other assets	(1,499)	(954)
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	0	0
Total assets	(11,527,525)	(11,432,183)
Liabilities:
Debt, net	(113,240)	(185,240)
Accounts payable, accrued expenses, and accrued capital expenditures	(1,499)	(954)
Advances from affiliates	(7,664,388)	(7,423,624)
Deferred income	0	0
Intangible lease liabilities, net	0	0
Interest rate swaps	0	0
Total liabilities	(7,779,127)	(7,609,818)
Stockholders’ Equity:
Common stock	0	0
Additional paid-in capital	(3,814,320)	(3,879,003)
Cumulative distributions in excess of earnings	65,922	56,638
Other comprehensive income	0	0
Piedmont stockholders’ equity	(3,748,398)	(3,822,365)
Noncontrolling interest	0	0
Total stockholders’ equity	(3,748,398)	(3,822,365)
Total liabilities and stockholders’ equity	$ (11,527,525)	$ (11,432,183)