Regulatory Matters (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended	1 Months Ended			0 Months Ended				1 Months Ended
	May 13, 2014 Tennessee Regulatory Authority [Member] Integrity Management Rider [Member]	Aug. 31, 2013 Tennessee Regulatory Authority [Member] Actual Cost Adjustment [Member]	Feb. 28, 2014 Tennessee Regulatory Authority [Member] Amortization And Refund For Excess Deferred Taxes [Member]	Aug. 31, 2014 Subsequent Event [Member] North Carolina Utilities Commission [Member] North Carolina Public Staff Audit 2014 Gas Cost Review Period [Member]	Aug. 11, 2014 Subsequent Event [Member] North Carolina Utilities Commission [Member] Emergency Service and Unauthorized Gas [Member]	Aug. 12, 2014 Subsequent Event [Member] Public Service Commission of South Carolina [Member] Purchased Gas Adjustment [Member]	Sep. 03, 2014 Subsequent Event [Member] Public Service Commission of South Carolina [Member] South Carolina Rate Stabilization Act [Member]	Aug. 21, 2014 Subsequent Event [Member] Public Service Commission of South Carolina [Member] Emergency Service [Member]	Aug. 31, 2014 Subsequent Event [Member] Tennessee Regulatory Authority [Member] Tennessee Incentive Plan [Member]	Sep. 30, 2014 Subsequent Event [Member] Tennessee Regulatory Authority [Member] CNG Infrastructure Rider [Member]
Public Utilities, General Disclosures [Line Items]
Public Utilities, Disclosure of Rate Matters				In August 2014, we filed testimony with the NCUC in support of our gas cost purchasing and accounting practices for the twelve months ended May 31, 2014. A hearing has been scheduled for October 7, 2014. We are waiting on a ruling from the NCUC at this time.	In April 2014, we filed a petition with the North Carolina Utilities Commission (NCUC) for a limited waiver of certain billing provisions of our tariff related to emergency service and unauthorized gas taken by customers in January 2014. A hearing was held on June 17, 2014. On August 11, 2014, we and the NCUC Public Staff filed a joint stipulation of settlement. The terms of the settlement include the granting of a waiver of the commodity index pricing mechanism for January 2014, that we should not be penalized for our conduct in varying from the tariff in this instance as that conduct was solely for the benefit of our customers, and that we and the Public Staff would work together to develop mutually agreeable revisions to our tariff to address the situation that led to this petition. We are waiting on a ruling from the NCUC at this time.	In June 2014, we filed testimony with the Public Service Commission of South Carolina (PSCSC) in support of our annual review of purchased gas adjustment (PGA) and gas purchasing policies for the twelve months ended March 31, 2014. In July 2014, a settlement agreement with the Office of Regulatory Staff (ORS) was filed in this matter. On August 6, 2014, the PSCSC approved the settlement agreement, finding that our gas purchasing policies and practices were reasonable and prudent, that we properly adhered to the gas cost recovery provisions of our tariff and relevant PSCSC orders and that we managed our hedging program in a manner consistent with PSCSC orders. The PSCSC issued its order on this matter on August 12, 2014.	In June 2014, we filed with the PSCSC a quarterly monitoring report for the twelve months ended March 31, 2014 and a cost and revenue study under the Rate Stabilization Act requesting a change in rates. On September 3, 2014, a settlement agreement with the ORS was filed with the PSCSC that stipulates a $2.9 million annual decrease in margin based on a return on equity of 10.2%, effective November 1, 2014. We are waiting on a ruling from the PSCSC at this time.	In July 2014, we filed a petition with the PSCSC requesting a limited waiver of certain billing provisions of our tariff related to emergency service for customers in January 2014. On August 6, 2014, the PSCSC granted our request and ordered us to continue to collaborate with the ORS to revise our tariff to address the situation that led to this petition. The PSCSC issued its written order on this matter on August 21, 2014.	In August 2014, we filed an annual report with the TRA reflecting the shared gas cost savings from gains and losses derived from gas purchase benchmarking and secondary market transactions for the twelve months ended June 30, 2014 under the Tennessee Incentive Plan (TIP). We are waiting on a ruling from the TRA at this time.	In September 2014, we filed a petition with the TRA seeking authority to implement a compressed natural gas infrastructure rider to recover the costs of our capital investments in infrastructure and equipment associated with this alternative motor vehicle transportation fuel. We proposed that the rider be effective October 1, 2014 with an initial rate adjustment on November 1, 2014 based on capital expenditures incurred through June 2014 and for rates to be updated annually outside of general rate cases for the return of and on these capital investments. We are waiting on a ruling from the TRA at this time.
Public Utilities, Rate Matters, Requested [Abstract]
Public Utilities Requested Rate Increase (Decrease) Amount		$ 3.7	$ (4.7)				$ (2.9)
Public Utilities, Requested Return on Equity, Percentage							10.20%
Public Utilities, Rate Matters, Approved [Abstract]
Public Utilities Approved Rate Increase (Decrease) Amount	$ 13.1