Acquisition of HV Bancorp, Inc., Summary of Purchase of HVB Acquisition (Details) - USD ($) $ / shares in Units, $ in Thousands		Jun. 16, 2023	Sep. 30, 2023	Dec. 31, 2022
Fair Value of Liabilities Assumed [Abstract]
Goodwill	[1]		$ 84,758	$ 31,376
HV Bancorp, Inc. [Member]
Purchase Price Consideration in Common Stock [Abstract]
Citizens Financial Services, Inc. shares issued (in shares)		693,858
Value assigned to Citizens Financial Services, Inc. common share (in dollars per share)		$ 86.67
Purchase price assigned to HVBC common shares exchanged for Citizens Financial Services, Inc.		$ 60,137
Purchase Price Consideration - Cash for Common Stock [Abstract]
Purchase price assigned to HVBC's common shares exchanged for cash		13,112
Purchase Price Related to Cash Payout of Stock Options		3,416
Total Purchase Price		76,665
Net Assets Acquired [Abstract]
HVBC shareholders equity		40,630
Adjustments to Reflect Assets Acquired at Fair Value [Abstract]
Investment		31
Loans [Abstract]
Interest rate		(24,097)
General credit		(1,834)
Credit - PCD Loans		(2,042)
Core deposit intangible		2,770
Owned premises		67
Other assets		(193)
Deferred tax asset		3,737
Fair Value of Liabilities Assumed [Abstract]
Time deposits		586
Borrowings		3,017
Other liabilities		611
Total fair value of identifiable net assets		23,283
Goodwill		$ 53,382	$ 53,382

[1] Excludes fully amortized intangible assets