Debt (Details) (USD $)	3 Months Ended		0 Months Ended
	Mar. 31, 2015 period		Apr. 10, 2015	Dec. 31, 2014		Jun. 27, 2014
Debt Instrument [Line Items]
Weighted Average Rate	3.31%	[1],[2]
Amount Outstanding	$ 2,326,109,000	[2]		$ 2,277,589,000	[2]
Maximum extension period	1 year
Number of extension periods	2
Extension period	6 months
$170 Million Unsecured Term Loan [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Rate	1.125%
Basis spread on variable rate	1.00%
LIBOR rate in effect	0.18%
Secured Debt [Member]
Debt Instrument [Line Items]
Weighted Average Rate	5.56%	[1],[2]
Amount Outstanding	448,791,000	[2]		449,045,000	[2]
Secured Debt [Member] | Fixed-Rate $105 Million Loan [Member]
Debt Instrument [Line Items]
Face amount of debt instrument	105,000,000
Rate	5.29%	[1],[3]
Amount Outstanding	105,000,000	[3]		105,000,000	[3]
Secured Debt [Member] | Fixed-Rate $105 Million Loan [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Amount repaid			105,000,000
Secured Debt [Member] | Fixed-Rate $125 Million Loan [Member]
Debt Instrument [Line Items]
Face amount of debt instrument	125,000,000
Rate	5.50%	[1],[4]
Amount Outstanding	125,000,000	[4]		125,000,000	[4]
Secured Debt [Member] | Fixed-Rate $42.5 Million Loan [Member]
Debt Instrument [Line Items]
Face amount of debt instrument	42,500,000.0
Rate	5.70%	[1]
Amount Outstanding	42,525,000			42,525,000
Secured Debt [Member] | WDC Mortgage Notes $140 Million[Member]
Debt Instrument [Line Items]
Face amount of debt instrument	140,000,000
Rate	5.76%	[1]
Amount Outstanding	140,000,000			140,000,000
Secured Debt [Member] | Mortgage Loan Maturing September 1, 2021 [Member]
Debt Instrument [Line Items]
Face amount of debt instrument	35,000,000					35,000,000.0
Rate	5.55%	[1],[5]
Amount Outstanding	36,266,000	[5]		36,520,000	[5]
Effective interest rate	3.75%
Unsecured Debt [Member]
Debt Instrument [Line Items]
Weighted Average Rate	2.78%	[1],[2]
Amount Outstanding	1,877,318,000	[2]		1,828,544,000	[2]
Unsecured Debt [Member] | $300 Million 2011 Unsecured Term Loan Maturing 2020 [Member]
Debt Instrument [Line Items]
Amount Outstanding	298,996,000	[6]		298,944,000	[6]
Unsecured Debt [Member] | $300 Million 2011 Unsecured Term Loan Maturing 2020 [Member] | Interest Rate Swap [Member]
Debt Instrument [Line Items]
Effective interest rate	3.35%
Unsecured Debt [Member] | $500 Million Unsecured Line of Credit [Member]
Debt Instrument [Line Items]
Face amount of debt instrument	500,000,000
Amount Outstanding	363,000,000	[7],[8]		434,000,000	[7],[8]
Basis spread on variable rate	1.175%
LIBOR rate in effect	0.18%
Unsecured Debt [Member] | $500 Million Unsecured Line of Credit [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	1.175%	[1],[7]
Unsecured Debt [Member] | $350 Million Senior Notes [Member]
Debt Instrument [Line Items]
Face amount of debt instrument	350,000,000
Rate	3.40%	[1],[9]
Amount Outstanding	348,831,000	[9]		348,800,000	[9]
Effective interest rate	3.45%
Unsecured Debt [Member] | $300 million Unsecured 2013 Term Loan Maturing 2019 [Member]
Debt Instrument [Line Items]
Face amount of debt instrument	300,000,000
Amount Outstanding	300,000,000	[10]		300,000,000	[10]
Unsecured Debt [Member] | $300 million Unsecured 2013 Term Loan Maturing 2019 [Member] | Interest Rate Swap [Member]
Debt Instrument [Line Items]
Effective interest rate	2.78%
Unsecured Debt [Member] | $300 million Unsecured 2013 Term Loan Maturing 2019 [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	1.20%	[1],[10]
Unsecured Debt [Member] | $400 Million Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Face amount of debt instrument	400,000,000
Rate	4.45%	[1],[11]
Amount Outstanding	396,914,000	[11]		396,832,000	[11]
Unsecured Debt [Member] | $50 Million Unsecured Term Loan [Member]
Debt Instrument [Line Items]
Face amount of debt instrument	50,000,000
Amount Outstanding	0			49,968,000
Unsecured Debt [Member] | $50 Million Unsecured Term Loan [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	1.15%	[1]
Unsecured Debt [Member] | $170 Million Unsecured Term Loan [Member]
Debt Instrument [Line Items]
Face amount of debt instrument	170,000,000
Amount Outstanding	169,577,000	[12]		0	[12]
Unsecured Debt [Member] | $170 Million Unsecured Term Loan [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	1.125%	[1],[12]
Unsecured Debt [Member] | $300 Million 2011 Unsecured Term Loan Maturing 2016 [Member]
Debt Instrument [Line Items]
Face amount of debt instrument	300,000,000
Unsecured Debt [Member] | $300 Million 2011 Unsecured Term Loan Maturing 2016 [Member] | Interest Rate Swap [Member]
Debt Instrument [Line Items]
Effective interest rate	2.39%
Unsecured Debt [Member] | $300 Million 2011 Unsecured Term Loan Maturing 2016 [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt Instrument [Line Items]
Basis spread on variable rate	1.15%	[1],[6]
Senior Notes [Member] | $350 Million Senior Notes [Member]
Debt Instrument [Line Items]
Effective interest rate	3.43%
Senior Notes [Member] | $400 Million Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Face amount of debt instrument	$ 400,000,000
Effective interest rate	4.48%
Effective interest rate	4.10%

[1] Other than the $35 Million Fixed-Rate Loan, all of Piedmont’s outstanding debt as of March 31, 2015 and December 31, 2014 is interest-only.

[2] Weighted average is based on contractual balance of outstanding debt and interest rates in the table as of March 31, 2015.

[3] On April 10, 2015, Piedmont repaid in full the balance on the $105 Million Fixed-Rate Loan.

[4] Property collateralized pool includes 1430 Enclave Parkway in Houston, Texas, Windy Point I and II in Schaumburg, Illinois, and 1055 East Colorado Boulevard in Pasadena, California.

[5] The $35 Million Fixed-Rate Loan has a contractual fixed rate of 5.55% ; however, the amortization of the premium recorded in order to adjust the note to its estimated fair value, results in an effective interest rate of 3.75%.

[6] The $300 Million Unsecured 2011 Term Loan has a stated variable rate; however, Piedmont has entered into interest rate swap agreements which effectively fix, exclusive of changes to Piedmont's credit rating, the rate on this facility to 2.39% through the original maturity date of November 22, 2016 and 3.35% from November 22, 2016 to January 15, 2020.

[7] Piedmont may select from multiple interest rate options with each draw, including the prime rate and various-length LIBOR locks. All LIBOR selections are subject to an additional spread (1.175% as of March 31, 2015) over the selected rate based on Piedmont’s current credit rating. The outstanding balance as of March 31, 2015 consisted of 30-day LIBOR draws at a rate of 0.18% (subject to the additional spread mentioned above).

[8] Piedmont may extend the term for up to one additional year (through two available six month extensions to a final extended maturity date of August 21, 2017) provided Piedmont is not then in default and upon payment of extension fees.

[9] The $350 Million Senior Notes have a fixed coupon rate of 3.40%, however, as a result of the issuance of the notes at a discount, Piedmont recognizes an effective interest rate on this debt issuance of 3.45%. After consideration of the impact of settled interest rate swap agreements, in addition to the issuance discount, the effective interest rate on this debt is 3.43%.

[10] The $300 Million Unsecured 2013 Term Loan has a stated variable rate; however, Piedmont entered into interest rate swap agreements which effectively fix, absent any changes to Piedmont's credit rating, the rate on this facility to 2.78% .

[11] The $400 Million Senior Notes have a fixed coupon rate of 4.45%, however, as a result of the issuance of the notes at a discount, Piedmont recognizes an effective interest rate on this debt issuance of 4.48%. After consideration of the impact of settled interest rate swap agreements, in addition to the issuance discount, the effective interest rate on this debt is 4.10%.

[12] Piedmont may select from multiple interest rate options, including the prime rate and various-length LIBOR locks. All LIBOR selections are subject to an additional spread (1.125% as of March 31, 2015) over the selected rate based on Piedmont’s current credit rating. The outstanding balance as of March 31, 2015 consisted of a 30-day LIBOR draw at a rate of 0.18% (subject to the additional spread mentioned above).