Document And Entity Information (USD $)	12 Months Ended
	Oct. 31, 2012	Dec. 14, 2012	Apr. 30, 2012
Document And Entity Information [Abstract]
Entity Registrant Name	PIEDMONT NATURAL GAS CO INC
Entity Central Index Key	0000078460
Document Type	10-K
Document Period End Date	Oct. 31, 2012
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2012
Amendment Flag	false
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Current Fiscal Year End Date	--10-31
Entity Filer Category	Large Accelerated Filer
Entity Well Known Seasoned Issuer	Yes
Entity Common Stock Shares Outstanding		72,276,272
Entity Public Float			$ 2,166,959,354