Stock Based Compensation (Outstanding Employee Deferred Stock Awards) (Details)		Jun. 30, 2015 employee $ / shares shares	May. 01, 2015 $ / shares shares	Dec. 31, 2014 $ / shares shares	May. 09, 2014 $ / shares shares	Jan. 03, 2014 $ / shares shares	Apr. 02, 2013 $ / shares shares	Apr. 04, 2012 $ / shares shares
Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant Date Fair Value | $ / shares		$ 17.86		$ 18.12
Unvested Shares		778,856		506,404
Stock Awards, Granted April 4 2012 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted	[1]							20,121
Grant Date Fair Value | $ / shares								$ 17.80
Of the shares granted, % vested		25.00%
Of the shares granted, % expected to vest in one year		25.00%
Of the shares granted, % expected to vest in two years		25.00%
Of the shares granted, % expected to vest in three years		25.00%
Unvested Shares	[2]	6,770
Number of employees | employee		2
Stock Awards, Granted April 2, 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted	[1]						118,174
Grant Date Fair Value | $ / shares							$ 19.47
Of the shares granted, % vested		25.00%
Of the shares granted, % expected to vest in one year		25.00%
Of the shares granted, % expected to vest in two years		25.00%
Of the shares granted, % expected to vest in three years		25.00%
Unvested Shares		38,065
Stock Awards 2, Granted April 2, 2013 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted	[1]						0
Grant Date Fair Value | $ / shares							$ 18.91
Unvested Shares	[3]	0
Stock Awards, Granted January 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted	[1]					95,476
Grant Date Fair Value | $ / shares						$ 16.45
Of the shares granted, % expected to vest in one year		20.00%
Of the shares granted, % expected to vest in two years		20.00%
Of the shares granted, % expected to vest in three years		20.00%
Of the shares granted, % expected to vest in four years		20.00%
Of the shares granted, % expected to vest in five years		20.00%
Unvested Shares		82,673
Stock Awards, Granted May 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted	[1]				163,163
Grant Date Fair Value | $ / shares					$ 18.47
Of the shares granted, % vested		25.00%
Of the shares granted, % expected to vest in one year		25.00%
Of the shares granted, % expected to vest in two years		25.00%
Of the shares granted, % expected to vest in three years		25.00%
Unvested Shares		97,762
Stock Awards 2, Granted May 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted	[1]				0
Grant Date Fair Value | $ / shares					$ 18.51
Unvested Shares	[4]	159,271
Stock Awards, Granted May 2015 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted	[1]		271,228
Grant Date Fair Value | $ / shares			$ 17.59
Of the shares granted, % vested		25.00%
Of the shares granted, % expected to vest in one year		25.00%
Of the shares granted, % expected to vest in two years		25.00%
Of the shares granted, % expected to vest in three years		25.00%
Unvested Shares		222,484
Stock Awards 2, Granted May 2015 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted	[1]		0
Grant Date Fair Value | $ / shares			$ 17.59
Unvested Shares	[4]	171,831

[1] Amounts reflect the total grant to employees, net of shares surrendered upon vesting to satisfy required minimum tax withholding obligations through June 30, 2015.

[2] Unvested shares outstanding represent grants made to two employees beginning their employment in 2012 subsequent to April 4, 2012, and such shares will fully vest by November 7, 2015.

[3] Estimated based on Piedmont's cumulative total stockholder return ("TSR") for the respective performance period through June 30, 2015. As of June 30, 2015, Piedmont's TSR for the fiscal year 2013-2015 performance share program was below threshold. Share estimates are subject to change in future periods based on both Piedmont's and its peers' stock performance and dividends paid.

[4] Estimated based on Piedmont's cumulative TSR for the respective performance period through June 30, 2015. Share estimates are subject to change in future periods based on both Piedmont's and its peers' stock performance and dividends paid.