Document And Entity Information - shares	9 Months Ended
	Jul. 31, 2016	Sep. 01, 2016
Document And Entity Information [Abstract]
Entity Registrant Name	PIEDMONT NATURAL GAS CO INC
Entity Central Index Key	0000078460
Document Type	10-Q
Document Period End Date	Jul. 31, 2016
Document Fiscal Period Focus	Q3
Document Fiscal Year Focus	2016
Amendment Flag	false
Current Fiscal Year End Date	--10-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock Shares Outstanding		83,090,909
Trading Symbol	PNY