Document And Entity Information	3 Months Ended
	Mar. 31, 2019
Document And Entity Information
Entity Central Index Key	0001462103
Entity Registrant Name	MEWBOURNE ENERGY PARTNERS 09-A, L.P.
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Current Fiscal Year End Date	--12-31
Amendment Flag	false
Entity Filer Category	Non-accelerated Filer
Is Entity's Reporting Status Current?	Yes
Document Fiscal Period Focus	Q1
Document Fiscal Year Focus	2019
Entity Emerging Growth Company	false
Entity Small Business	true