Junior Subordinated Debentures - Issuance (Details) - USD ($) $ in Thousands		1 Months Ended	6 Months Ended	7 Months Ended	12 Months Ended
	Feb. 24, 2020	Apr. 30, 2007	Jun. 15, 2017	Dec. 31, 2017	Dec. 31, 2022	Dec. 31, 2021
Junior subordinated debentures
Cash distribution rate of trust preferred securities (as a percent)	7.80%
Junior subordinated debentures					$ 25,773	$ 25,773
Junior Subordinated Debentures issuance cost					$ 1	$ 1
Old Second Capital Trust II [Member]
Junior subordinated debentures
Proceeds from sale of cumulative trust preferred securities		$ 25,000
Maturity Period					30 years
Cash distribution fixed rate of trust preferred securities (as a percent)			6.77%
Basis points added to cash distribution floating rate base (as a percent)				1.50%
Cash distribution, floating rate base					three-month LIBOR
Junior subordinated debentures | Old Second Capital Trust I
Junior subordinated debentures
Interest rate (as a percent)					4.42%	4.36%
Junior subordinated debentures | Old Second Capital Trust II [Member]
Junior subordinated debentures
Junior subordinated debentures					$ 25,800