Variable Interest Entities (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Eye Street 1201 NW Associates LLC [Member]
Variable Interest Entity [Line Items]
Piedmont’s % Ownership of Entity	49.50%
Net Carrying Amount	$ (2.5)	$ (5.3)
Variable interest entity, cash flow percent entitled to entity	100.00%
Eye Street 1225 NW Associates LLC [Member]
Variable Interest Entity [Line Items]
Piedmont’s % Ownership of Entity	49.50%
Net Carrying Amount	(1.8)	(0.9)
Variable interest entity, cash flow percent entitled to entity	100.00%
Piedmont 500 W. Monroe Fee LLC [Member]
Variable Interest Entity [Line Items]
Piedmont’s % Ownership of Entity	100.00%
Net Carrying Amount	240.3	228.3
Suwanee Gateway One LLC [Member]
Variable Interest Entity [Line Items]
Piedmont’s % Ownership of Entity	100.00%
Net Carrying Amount	7.2	7.4
Medici Atlanta LLC [Member]
Variable Interest Entity [Line Items]
Piedmont’s % Ownership of Entity	100.00%
Net Carrying Amount	15.3	14.4
TownPark 400, LLC [Member]
Variable Interest Entity [Line Items]
Piedmont’s % Ownership of Entity	100.00%
Net Carrying Amount	$ 22.2	$ 22.3