Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Nov. 07, 2019
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Document Fiscal Period Focus	Q3
Document Fiscal Year Focus	2019
Trading Symbol	MPB
Entity Registrant Name	MID PENN BANCORP INC
Entity Central Index Key	0000879635
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		8,478,461
Entity Current Reporting Status	Yes
Entity Shell Company	false
Entity File Number	1-13677
Entity Tax Identification Number	25-1666413
Entity Address, Address Line One	349 Union Street
Entity Address, City or Town	Millersburg
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	17061
City Area Code	1.866
Local Phone Number	642.7736
Entity Interactive Data Current	Yes
Entity Incorporation, State or Country Code	PA
Title of 12(b) Security	Common Stock, $1.00 par value per share
Security Exchange Name	NASDAQ
Document Quarterly Report	true
Document Transition Report	false