Document And Entity Information - USD ($)	12 Months Ended
	Sep. 30, 2020	Oct. 31, 2020	Mar. 31, 2020
Cover [Abstract]
Amendment Flag	false
Current Fiscal Year End Date	--09-30
Document Annual Report	true
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2020
Document Period End Date	Sep. 30, 2020
Documents Incorporated by Reference	Portions of the registrant’s definitive Proxy Statement for its 2021 Annual Meeting of Stockholders, to be filed with the Securities and Exchange Commission within 120 days of September 30, 2020, are incorporated by reference into Part III of this report.
Document Transition Report	false
Document Type	10-K
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		90,965,576
Entity Current Reporting Status	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 Interactive Data Current	Yes
Entity Public Float			$ 3,219,563,000
Entity Listing, Par Value Per Share	$ 1.00
Entity Registrant Name	National Fuel Gas Company
Entity Shell Company	false
Entity Small Business	false
Entity Tax Identification Number	13-1086010
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	Yes
City Area Code	716
Local Phone Number	857-7000
Title of 12(b) Security	Common Stock, par value $1.00 per share
Security Exchange Name	NYSE
Trading Symbol	NFG
ICFR Auditor Attestation Flag	true