Borrowings - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
FHLB advances, maturity due 2020	$ 451,000
FHLB advances, maturity due 2021	5,000
FHLB advances, maturity due 2022	10,000
FHLB advances, maturity due 2023	10,000
FHLB advances, maturity due 2024	$ 10,000
Period for Interest Deferral on Trust Preferred Securities	5 years
Securities sold under repurchase agreements	$ 1,961	$ 2,999
Maturity Overnight [Member]
Debt Instrument [Line Items]
Securities sold under repurchase agreements	2,000	3,000
Maturity Overnight [Member] | Collateralized mortgage obligations [Member]
Debt Instrument [Line Items]
Investment securities under repurchase agreement, market value	5,600	$ 5,800
First Defiance Statutory Trusts II [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Trust Preferred Securities	15,000
Proceeds from Issuance of Subordinated Long-term Debt	$ 15,500
Coupon Rate on Preferred Securities, Period End	2.24%	4.29%
Preferred Securities Variable Interest Rate	LIBOR rate plus 1.5%
Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Description	The Trust Preferred Securities and Subordinated Debentures mature on June 15, 2037, but can be redeemed at the Company’s option at any time now.
First Defiance Statutory Trusts I [Member]
Debt Instrument [Line Items]
Proceeds from Issuance of Trust Preferred Securities	$ 20,000
Proceeds from Issuance of Subordinated Long-term Debt	$ 20,600
Coupon Rate on Preferred Securities, Period End	2.12%	4.17%
Preferred Securities Variable Interest Rate	LIBOR rate plus 1.38%
Financial Instruments Subject to Mandatory Redemption, Settlement Terms, Description	The Trust Preferred Securities and Subordinated Debentures mature on December 15, 2035, but can be redeemed at the Company’s option at any time now.