Document and Entity Information Document	3 Months Ended
	Mar. 31, 2020 shares
Entity Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2020
Document Transition Report	false
Entity File Number	1-12579
Entity Registrant Name	OGE ENERGY CORP.
Entity Incorporation, State or Country Code	OK
Entity Tax Identification Number	73-1481638
Entity Central Index Key	0001021635
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Amendment Flag	false
Title of 12(b) Security	Common Stock
Trading Symbol	OGE
Security Exchange Name	NYSE
Entity Filer Category	Large Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Address, Address Line One	321 North Harvey
Entity Address, Address Line Two	P.O. Box 321
Entity Address, City or Town	Oklahoma City
Entity Address, State or Province	OK
Entity Address, Postal Zip Code	73101-0321
City Area Code	405
Local Phone Number	553-3000
Entity Common Stock, Shares Outstanding	200,169,431