Merger (Narrative) (Details) - USD ($)		3 Months Ended		9 Months Ended		12 Months Ended
	Apr. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Apr. 29, 2018
Business Acquisition [Line Items]
Fair value gain				$ 415,000
Acquiree's common shares outstanding		5,093,536		5,093,536		4,767,656
Goodwill		$ 9,139,000		$ 9,139,000		$ 5,448,000
Income/gain from unconsolidated subsidiary			$ 49,000	$ 296,000	$ 154,000
Federal statutory tax rate				21.00%		34.00%
Liverpool Community Bank [Member]
Business Acquisition [Line Items]
Acquisition date	Apr. 30, 2018
Business acquisition, name of acquired entity				Liverpool Community Bank
Total assets of acquiree	$ 45,360,000
Loans receivables of acquiree	32,091,000
Equity of acquiree	$ 9,246,000
Percentage of equity interest in acquiree, before acquisition							39.16%
Percentage of equity interest acquired	60.84%
Number of acquiree's common shares owned							1,214
Equity owned before acquisition	$ 4,622,000
Juniata's basis in Liverpool	5,037,000
Fair value gain	$ 415,000
Per share price of Liverpool shares	$ 4,050.00
Acquiree's common shares outstanding							3,100
Number of Juniata's share for each Liverpool share	202.6286
Number of shares issued upon the closing of acquisition	315,284
Fair value of shares issued for acquisition	$ 6,463,000
Closing stock price	$ 20.50
Approximate cash transaction of business acquisition	$ 1,362,000
Juniata's Step One adjusted basis in Liverpool	12,862,000
Step Two purchase price consideration	7,825,000
Goodwill	3,691,000
Core deposit intangible assets acquired	289,000
Intangible assets amortization period				10 years
Gross amortized cost basis	$ 32,091,000
Income/gain from unconsolidated subsidiary			49,000	$ 296,000	154,000
Merger related costs		185,000		625,000
Merger related tax expense (benefit)		$ (39,000)	$ (49,000)	$ (69,000)	$ (163,000)
Federal statutory tax rate		21.00%	21.00%	21.00%	21.00%
Minimum [Member] | Liverpool Community Bank [Member]
Business Acquisition [Line Items]
Percentage of outstanding common stock to be purchased for cash	15.00%
Maximum [Member] | Liverpool Community Bank [Member]
Business Acquisition [Line Items]
Percentage of outstanding common stock to be purchased for cash	20.00%