Document And Entity Information - $ / shares	6 Months Ended
	Mar. 31, 2021	Apr. 30, 2021
Cover [Abstract]
Amendment Flag	false
Current Fiscal Year End Date	--09-30
Document Fiscal Period Focus	Q2
Document Fiscal Year Focus	2021
Document Period End Date	Mar. 31, 2021
Document Quarterly Report	true
Document Transition Report	false
Document Type	10-Q
Entity Address, Address Line One	6363 Main Street
Entity Address, City or Town	Williamsville,
Entity Address, State or Province	NY
Entity Address, Postal Zip Code	14221
Entity Central Index Key	0000070145
Entity Common Stock, Shares Outstanding		91,172,701
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Emerging Growth Company	false
Entity File Number	1-3880
Entity Filer Category	Large Accelerated Filer
Entity Incorporation, State or Country Code	NJ
Entity Registrant Name	NATIONAL FUEL GAS COMPANY
Entity Shell Company	false
Entity Small Business	false
Entity Tax Identification Number	13-1086010
City Area Code	716
Local Phone Number	857-7000
Title of 12(b) Security	Common Stock, par value $1.00 per share
Trading Symbol	NFG
Security Exchange Name	NYSE
Entity Listing, Par Value Per Share	$ 1.00