Debt (Details)		12 Months Ended
		Dec. 31, 2016 USD ($) period		Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Debt Instrument [Line Items]
Weighted average interest rate	[1]	3.43%	[2]	3.55%
Amount of indebtedness outstanding	[1],[2]	$ 2,020,475,000		$ 2,029,510,000
Interest payments		$ 69,000,000		76,400,000	$ 72,100,000
Secured Debt [Member]
Debt Instrument [Line Items]
Weighted average interest rate	[1],[2]	4.64%
Amount of indebtedness outstanding	[1],[2]	$ 332,744,000		501,289,000
Net premium, discounts, and unamortized debt issuance costs	[1]	$ 1,161,000		1,319,000
Unsecured Debt [Member]
Debt Instrument [Line Items]
Weighted average interest rate	[1],[2]	3.19%
Amount of indebtedness outstanding	[1],[2]	$ 1,687,731,000		1,528,221,000
Net premium, discounts, and unamortized debt issuance costs	[1]	(10,269,000)		(12,779,000)
$125.0 Million Fixed-Rate Loan [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Amount of principal paid off		$ 125,000,000
Interest rate percentage	[1]	5.50%
Effective rate percentage	[1],[3]	5.50%
Amount of indebtedness outstanding	[1]	$ 0		125,000,000
Face amount of facility		125,000,000
$42.5 Million Fixed-Rate Loan [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Amount of principal paid off		$ 42,500,000
Interest rate percentage	[1]	5.70%
Effective rate percentage	[1],[3]	5.70%
Amount of indebtedness outstanding	[1]	$ 0		42,525,000
Face amount of facility		42,500,000
$500 Million Unsecured 2015 Line of Credit [Member] | Unsecured Debt [Member] | Line of Credit [Member]
Debt Instrument [Line Items]
Amount of line of credit		500,000,000
Net borrowings incurred		$ 157,000,000
Effective rate percentage	[1],[3],[4]	1.74%
Amount of indebtedness outstanding	[1],[4],[5]	$ 178,000,000		21,000,000
Face amount of facility		$ 500,000,000
Additional extension period		1 year
Number of extension periods | period		2
Extension period		6 months
$500 Million Unsecured 2015 Line of Credit [Member] | Unsecured Debt [Member] | Line of Credit [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable percentage rate	[1],[4]	1.00%
$140 Million WDC Fixed-Rate Loans [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Interest rate percentage	[1],[6]	5.76%
Effective rate percentage	[1],[3],[6]	5.76%
Amount of indebtedness outstanding	[1],[6]	$ 140,000,000		140,000,000
Face amount of facility		$ 140,000,000
$35.0 Million Fixed-Rate Loan [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Interest rate percentage	[1],[7]	5.55%
Effective rate percentage	[1],[3],[7]	3.75%
Amount of indebtedness outstanding	[1],[7]	$ 31,583,000		32,445,000
Face amount of facility		$ 35,000,000
$160.0 Million Fixed Rate Loan [Member] | Secured Debt [Member]
Debt Instrument [Line Items]
Interest rate percentage	[1],[8]	3.48%
Effective rate percentage	[1],[3]	3.58%
Amount of indebtedness outstanding	[1],[8]	$ 160,000,000		160,000,000
Face amount of facility		$ 160,000,000
$170 Million Unsecured 2015 Term Loan [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Effective rate percentage	[1],[3],[4]	1.78%
Amount of indebtedness outstanding	[1],[4]	$ 170,000,000		170,000,000
Face amount of facility		$ 170,000,000
$170 Million Unsecured 2015 Term Loan [Member] | Unsecured Debt [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable percentage rate	[1],[4]	1.125%
$300 Million Unsecured 2013 Term Loan [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Amount of indebtedness outstanding	[1]	$ 300,000,000		300,000,000
Face amount of facility		$ 300,000,000
$300 Million Unsecured 2013 Term Loan [Member] | Unsecured Debt [Member] | Interest Rate Swap [Member]
Debt Instrument [Line Items]
Effective rate percentage	[1],[3]	2.78%
$300 Million Unsecured 2013 Term Loan [Member] | Unsecured Debt [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable percentage rate	[1]	1.20%
$300 Million Unsecured 2011 Term Loan [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Amount of indebtedness outstanding	[1]	$ 300,000,000		300,000,000
Face amount of facility		$ 300,000,000
$300 Million Unsecured 2011 Term Loan [Member] | Unsecured Debt [Member] | Interest Rate Swap [Member]
Debt Instrument [Line Items]
Effective rate percentage	[1],[3]	3.35%
$300 Million Unsecured 2011 Term Loan [Member] | Unsecured Debt [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Basis spread on variable percentage rate	[1]	1.15%
$350 Million Unsecured Senior Notes [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Interest rate percentage	[1]	3.40%
Effective rate percentage	[1],[3]	3.43%
Amount of indebtedness outstanding	[1]	$ 350,000,000		350,000,000
Face amount of facility		$ 350,000,000
$400 Million Unsecured Senior Notes [Member] | Unsecured Debt [Member]
Debt Instrument [Line Items]
Interest rate percentage	[1]	4.45%
Effective rate percentage	[1],[3]	4.10%
Amount of indebtedness outstanding	[1]	$ 400,000,000		$ 400,000,000
Face amount of facility		$ 400,000,000

[1] Other than the $35 Million Fixed-Rate Loan, all of Piedmont’s outstanding debt as of December 31, 2016 and 2015 is interest-only.

[2] Weighted average is based on contractual balance of outstanding debt and the stated or effectively fixed interest rates in the table as of December 31, 2016.

[3] Effective rate after consideration of settled or in place interest rate swap agreements and/or issuance premiums or discounts.

[4] On a periodic basis, 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 over the selected rate based on Piedmont’s current credit rating.

[5] Piedmont may extend the term for up to one additional year (through two available six month extensions to a final extended maturity date of June 18, 2020) provided Piedmont is not then in default and upon payment of extension fees.

[6] Collateralized by the 1201 and 1225 Eye Street buildings in Washington, D.C.

[7] Collateralized by the 5 Wall Street building in Burlington, Massachusetts.

[8] Collateralized by the 1901 Market Street building in Philadelphia, Pennsylvania.