Stock Based Compensation (Outstanding Employee Stock Awards) (Details) - $ / shares		May 18, 2017	May 24, 2016	May 01, 2015	Jan. 03, 2014	Jun. 30, 2017	Dec. 31, 2016
Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant Date Fair Value (in dollars per share)						$ 21.94	$ 19.44
Unvested Shares (in shares)						968,883	944,223
Deferred Stock Awards [Member] | Deferred Stock Award, Granted January 3, 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted (in shares)	[1]				86,769
Grant Date Fair Value (in dollars per share)					$ 16.56
Unvested Shares (in shares)						35,094
Deferred Stock Awards [Member] | Deferred Stock Award, Granted January 3, 2014 [Member] | Share-based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage					20.00%
Deferred Stock Awards [Member] | Deferred Stock Award, Granted January 3, 2014 [Member] | Share-based Compensation Award, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage					20.00%
Deferred Stock Awards [Member] | Deferred Stock Award, Granted January 3, 2014 [Member] | Share-based Compensation Award, Tranche Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage					20.00%
Deferred Stock Awards [Member] | Deferred Stock Award, Granted January 3, 2014 [Member] | Share-based Compensation Award, Tranche Four [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage					20.00%
Deferred Stock Awards [Member] | Deferred Stock Award, Granted January 3, 2014 [Member] | Share-based Compensation Award, Tranche Five [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage					20.00%
Deferred Stock Awards [Member] | Deferred Stock Award, Granted May 1, 2015 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted (in shares)	[1]			216,919
Grant Date Fair Value (in dollars per share)				$ 17.59
Unvested Shares (in shares)						67,747
Deferred Stock Awards [Member] | Deferred Stock Award, Granted May 1, 2015 [Member] | Share-based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage				25.00%
Deferred Stock Awards [Member] | Deferred Stock Award, Granted May 1, 2015 [Member] | Share-based Compensation Award, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage				25.00%
Deferred Stock Awards [Member] | Deferred Stock Award, Granted May 1, 2015 [Member] | Share-based Compensation Award, Tranche Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage				25.00%
Deferred Stock Awards [Member] | Deferred Stock Award, Granted May 1, 2015 [Member] | Share-based Compensation Award, Tranche Four [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage				25.00%
Deferred Stock Awards [Member] | Deferred Stock Award, Granted May 24, 2016 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted (in shares)	[1]		233,073
Grant Date Fair Value (in dollars per share)			$ 19.91
Unvested Shares (in shares)						134,117
Deferred Stock Awards [Member] | Deferred Stock Award, Granted May 24, 2016 [Member] | Share-based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage			25.00%
Deferred Stock Awards [Member] | Deferred Stock Award, Granted May 24, 2016 [Member] | Share-based Compensation Award, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage			25.00%
Deferred Stock Awards [Member] | Deferred Stock Award, Granted May 24, 2016 [Member] | Share-based Compensation Award, Tranche Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage			25.00%
Deferred Stock Awards [Member] | Deferred Stock Award, Granted May 24, 2016 [Member] | Share-based Compensation Award, Tranche Four [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage			25.00%
Deferred Stock Awards [Member] | Deferred Stock Award, Granted May 18, 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted (in shares)	[1]	246,808
Grant Date Fair Value (in dollars per share)		$ 21.38
Unvested Shares (in shares)						202,233
Deferred Stock Awards [Member] | Deferred Stock Award, Granted May 18, 2017 [Member] | Board of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted (in shares)	[1]	26,187
Grant Date Fair Value (in dollars per share)		$ 21.38
Unvested Shares (in shares)						26,187
Deferred Stock Awards [Member] | Deferred Stock Award, Granted May 18, 2017 [Member] | Share-based Compensation Award, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		25.00%
Deferred Stock Awards [Member] | Deferred Stock Award, Granted May 18, 2017 [Member] | Share-based Compensation Award, Tranche One [Member] | Board of Directors [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		100.00%
Deferred Stock Awards [Member] | Deferred Stock Award, Granted May 18, 2017 [Member] | Share-based Compensation Award, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		25.00%
Deferred Stock Awards [Member] | Deferred Stock Award, Granted May 18, 2017 [Member] | Share-based Compensation Award, Tranche Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		25.00%
Deferred Stock Awards [Member] | Deferred Stock Award, Granted May 18, 2017 [Member] | Share-based Compensation Award, Tranche Four [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting percentage		25.00%
Performance Share Program Award [Member] | Performance Share Program Award, Granted May 1, 2015 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted (in shares)	[1]			0
Grant Date Fair Value (in dollars per share)				$ 18.42
Unvested Shares (in shares)	[2]					229,828
Performance Share Program Award [Member] | Performance Share Program Award, Granted May 24, 2016 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted (in shares)	[1]		0
Grant Date Fair Value (in dollars per share)			$ 23.02
Unvested Shares (in shares)	[2]					85,792
Performance Share Program Award [Member] | Performance Share Program Award, Granted May 18, 2017 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Shares Granted (in shares)	[1]	0
Grant Date Fair Value (in dollars per share)		$ 30.45
Unvested Shares (in shares)	[2]					187,885

[1] Amounts reflect the total grant to employees and independent directors, net of shares surrendered upon vesting to satisfy required minimum tax withholding obligations through June 30, 2017.

[2] Estimated based on Piedmont's cumulative TSR for the respective performance period through June 30, 2017. Share estimates are subject to change in future periods based on both Piedmont's and its peers' stock performance and dividends paid.