Employee Share Based Plans (Details) (USD $)	12 Months Ended											37 Months Ended	1 Months Ended	12 Months Ended	60 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2011	Oct. 31, 2013 Stock Compensation Plan [Member]	Oct. 31, 2013 Long Term Incentive Plan Two Performance Measures [Member] Stock Compensation Plan [Member]	Oct. 31, 2013 Long Term Incentive Plan Two Performance Measures [Member] Stock Compensation Plan [Member] EPS Performance [Member]	Oct. 31, 2013 Long Term Incentive Plan Two Performance Measures [Member] Stock Compensation Plan [Member] Annual Shareholder Return [Member]	Oct. 31, 2013 Long Term Incentive Plan Three Performance Measures [Member] Stock Compensation Plan [Member]	Oct. 31, 2013 Long Term Incentive Plan Three Performance Measures [Member] Stock Compensation Plan [Member] EPS Performance [Member]	Oct. 31, 2013 Long Term Incentive Plan Three Performance Measures [Member] Stock Compensation Plan [Member] Annual Shareholder Return [Member]	Oct. 31, 2013 Long Term Incentive Plan Three Performance Measures [Member] Stock Compensation Plan [Member] Return On Equity [Member]	Dec. 31, 2013 Retention Stock Unit Award Eligible Officers [Member] Stock Compensation Plan [Member]	Dec. 31, 2011 Retention Stock Unit Award President And Cheif Executive Officer [Member] Stock Compensation Plan [Member]	Oct. 31, 2013 Retention Stock Unit Award President And Cheif Executive Officer [Member] Stock Compensation Plan [Member]	Dec. 15, 2016 Retention Stock Unit Award President And Cheif Executive Officer [Member] Stock Compensation Plan [Member]
Employee Share Based Plans Details [Line Items]
Unvested Shares Issued To CEO													64,700
Incentive Compensation Plan Percentage Of Common Stock Vested														In accordance with the vesting schedule, 20% of the units vest on December 15, 2014, 30% of the units vest on December 15, 2015 and 50% of the units vest on December 15, 2016.
Compensation Expense	$ 4,526,000	$ 5,730,000	$ 2,604,000
Tax Benefit	1,538,000	2,080,000	673,000
Liability	11,098,000	10,631,000
Incentive Compensation Plan Expected Payout In One Year	4,071,000
Incentive Compensation Plan Expected Payout In Two Years	4,290,000
Incentive Compensation Plan Expected Payout In Three Years	2,290,000
Incentive Compensation Plan Expected Payout In Four Years	$ 446,000
Employee Stock Purchase Plan Exercise Price As A Percentage Of Fair Market Value	95.00%
Share Based Compensation Arrangement By Share Based Payment Award Description	Under our shareholder approved ICP, eligible officers and other participants are awarded units that pay out depending upon the level of performance achieved by Piedmont during three-year incentive plan performance periods. Distribution of those awards may be made in the form of shares of common stock and withholdings for payment of applicable taxes on the compensation. These plans require that a minimum threshold performance level be achieved in order for any award to be distributed. Also under our approved ICP, 64,700 unvested retention stock units were granted to our President and Chief Executive Officer in December 2011. At the time of distribution of awards under the ICP, the number of shares issuable is reduced by the withholdings for payment of applicable income taxes for each participant. The participant may elect income tax withholdings at or above the minimum statutory withholding requirements. The maximum withholdings allowed is 50%.													In December 2010, a long-term retention stock unit award under the ICP (where a stock unit equals one share of our common stock upon vesting) was approved for eligible officers and other participants to support our succession planning and retention strategies. This retention stock unit award will vest for participants who have met the retention requirements at the end of a three-year period ending in December 2013 in the form of shares of common stock and withholdings for payment of applicable taxes on the compensation. The Compensation Committee of our Board of Directors has the discretion to accelerate the vesting of all or a portion of a participant’s units.
Share Based Compensation Arrangement By Share Based Payment Award Award Requisite Service Period												3 years			5 years
Share Based Compensation Arrangement By Share Based Payment Award Terms Of Award					For each of these performance periods, awards will be based on achievement relative to a target annual compounded increase in basic EPS and the achievement of total shareholder returns relative to a group of peer companies that are domiciled in the United States, publicly traded in the U.S. energy industry with a primary focus on natural gas distribution and transmission businesses in multi-state territories and have similar annual revenues and market capitalization to ours, with each measure being weighted at 50%.			The plan with the performance period ending October 31, 2015 (2015 plan) has an additional performance measure of actual average return on equity compared to the weighted average return on equity allowed by our regulatory commissions. The weighting of the units awarded under the 2015 plan is based on EPS at 37.5%, total shareholder return at 37.5 % and return on equity at 25% of the total units awarded.						During the five-year vesting period, any dividend equivalents will accrue on these stock units and be converted into additional units at the same rate and based on the closing price on the same payment date as dividends on our common stock. The stock units will vest, payable in the form of shares of common stock and withholdings for payment of applicable taxes on the compensation, over a five-year period only if he is an employee on each vesting date.
Number Of Incentive Compensation Plan Awards				3
Number Of Performance Periods Under Icp Plans	3
Maximum Statutory Withholdings Allowed	50.00%
Allocation Of Performance Units						50.00%	50.00%		37.50%	37.50%	25.00%