Debt (Narrative) (Details) (USD $)	0 Months Ended	3 Months Ended			9 Months Ended
	May 09, 2013	Sep. 30, 2013		Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012
Debt Instrument [Line Items]
Percentage ownership in operating partnership	100.00%				99.90%
Settlement of forward starting interest rate swaps					$ (672,000)		$ 0
Interest payments on debt facilities		15,500,000		15,700,000	47,300,000		47,100,000
Interest Costs Capitalized					0
Senior Notes [Member] | $350 Million Senior Notes [Member]
Debt Instrument [Line Items]
Face amount of debt instument	350,000,000	350,000,000			350,000,000
Rate		3.40%	[1],[2]		3.40%	[1],[2]
Proceeds from debt	348,600,000
Discount on notes payable	1,400,000
Term of notes	10 years
Senior Notes [Member] | $350 Million Senior Notes [Member] | Forward Starting Interest Rate Swap [Member]
Debt Instrument [Line Items]
Number of Interest Rate Derivatives Settled During the Period					2
Notional amount of forward starting swap agreements	250,000,000
Settlement of forward starting interest rate swaps	700,000
Senior Notes [Member] | $350 Million Senior Notes [Member] | Forward Starting Rate Swap 1 [Member]
Debt Instrument [Line Items]
Notional amount of forward starting swap agreements	220,000,000
Senior Notes [Member] | $350 Million Senior Notes [Member] | Forward Starting Rate Swap 2 [Member]
Debt Instrument [Line Items]
Notional amount of forward starting swap agreements	30,000,000
Unsecured Debt [Member] | $500 Million Unsecured Line of Credit [Member]
Debt Instrument [Line Items]
Face amount of debt instument		500,000,000			500,000,000
Net borrowings					484,000,000
Repayments					426,000,000
Borrowing capacity of line of credit		$ 500,000,000			$ 500,000,000

[1] 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%.

[2] All of Piedmont’s outstanding debt as of September 30, 2013 and December 31, 2012 is interest-only debt.