OTHER BORROWINGS (Trust Preferred Offerings) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Less: deferred issuance costs	$ (40)
Total	371,753	$ 372,072
Trust preferred securities
Debt Instrument [Line Items]
Total trust preferred offerings	148,324
Total	148,284	$ 147,316
Heartland Financial Statutory Trust IV | Trust preferred securities
Debt Instrument [Line Items]
Total trust preferred offerings	$ 10,310
Interest rate (as a percent)	7.49%
Heartland Financial Statutory Trust V | Trust preferred securities
Debt Instrument [Line Items]
Total trust preferred offerings	$ 20,619
Interest rate (as a percent)	5.41%
Heartland Financial Statutory Trust VI | Trust preferred securities
Debt Instrument [Line Items]
Total trust preferred offerings	$ 20,619
Interest rate (as a percent)	6.25%
Heartland Financial Statutory Trust VII | Trust preferred securities
Debt Instrument [Line Items]
Total trust preferred offerings	$ 18,042
Interest rate (as a percent)	6.24%
Morrill Statutory Trust I | Trust preferred securities
Debt Instrument [Line Items]
Total trust preferred offerings	$ 9,370
Interest rate (as a percent)	7.97%
Morrill Statutory Trust II | Trust preferred securities
Debt Instrument [Line Items]
Total trust preferred offerings	$ 9,087
Interest rate (as a percent)	7.59%
Sheboygan Statutory Trust I | Trust preferred securities
Debt Instrument [Line Items]
Total trust preferred offerings	$ 6,790
Interest rate (as a percent)	7.69%
CBNM Capital Trust I | Trust preferred securities
Debt Instrument [Line Items]
Total trust preferred offerings	$ 4,558
Interest rate (as a percent)	8.02%
Citywide Capital Trust III | Trust preferred securities
Debt Instrument [Line Items]
Total trust preferred offerings	$ 6,605
Interest rate (as a percent)	7.22%
Citywide Capital Trust IV | Trust preferred securities
Debt Instrument [Line Items]
Total trust preferred offerings	$ 4,468
Interest rate (as a percent)	6.89%
Citywide Capital Trust V | Trust preferred securities
Debt Instrument [Line Items]
Total trust preferred offerings	$ 12,424
Interest rate (as a percent)	6.31%
OCGI Statutory Trust III | Trust preferred securities
Debt Instrument [Line Items]
Total trust preferred offerings	$ 3,020
Interest rate (as a percent)	8.48%
OCGI Capital Trust IV | Trust preferred securities
Debt Instrument [Line Items]
Total trust preferred offerings	$ 5,511
Interest rate (as a percent)	7.27%
BVBC Capital Trust II | Trust preferred securities
Debt Instrument [Line Items]
Total trust preferred offerings	$ 7,319
Interest rate (as a percent)	7.69%
BVBC Capital Trust III | Trust preferred securities
Debt Instrument [Line Items]
Total trust preferred offerings	$ 9,582
Interest rate (as a percent)	6.35%
LIBOR | Heartland Financial Statutory Trust IV | Trust preferred securities
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	2.75%
LIBOR | Heartland Financial Statutory Trust V | Trust preferred securities
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.33%
LIBOR | Heartland Financial Statutory Trust VI | Trust preferred securities
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.48%
LIBOR | Heartland Financial Statutory Trust VII | Trust preferred securities
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.48%
LIBOR | Morrill Statutory Trust I | Trust preferred securities
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	3.25%
LIBOR | Morrill Statutory Trust II | Trust preferred securities
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	2.85%
LIBOR | Sheboygan Statutory Trust I | Trust preferred securities
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	2.95%
LIBOR | CBNM Capital Trust I | Trust preferred securities
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	3.25%
LIBOR | Citywide Capital Trust III | Trust preferred securities
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	2.80%
LIBOR | Citywide Capital Trust IV | Trust preferred securities
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	2.20%
LIBOR | Citywide Capital Trust V | Trust preferred securities
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.54%
LIBOR | OCGI Statutory Trust III | Trust preferred securities
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	3.65%
LIBOR | OCGI Capital Trust IV | Trust preferred securities
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	2.50%
LIBOR | BVBC Capital Trust II | Trust preferred securities
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	3.25%
LIBOR | BVBC Capital Trust III | Trust preferred securities
Debt Instrument [Line Items]
Basis spread on variable rate (as a percent)	1.60%