The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

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Amount of hedged item in hedging relationship. Excludes hedged asset or liability.

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Amount, before tax and after reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness.

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DERIVATIVE FINANCIAL INSTRUMENTS (Cash flow hedges narrative) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	May 18, 2018
Derivative [Line Items]
Change in net unrealized losses and reclassification from AOCI to interest expense on cash flow hedges	$ 1.8
Estimated amount to be reclassified from accumulated other comprehensive income to interest expense	2.4
Interest Rate Swaps \| Cash Flow Hedges
Derivative [Line Items]
Derivative, notional amount	40.0		$ 9.0
Interest Rate Swaps \| Cash Flow Hedges \| Heartland Financial Statutory Trust IV, VI, And VII
Derivative [Line Items]
Derivative, notional amount	$ 40.0
Interest Rate Swaps \| Cash Flow Hedges \| Heartland Financial Statutory Trust IV
Derivative [Line Items]
Derivative, notional amount		$ 25.0
Interest Rate Swaps \| Cash Flow Hedges \| OCGI Statutory Trust III
Derivative [Line Items]
Derivative, notional amount			3.0
Interest Rate Swaps \| Cash Flow Hedges \| OCGI Capital Trust IV
Derivative [Line Items]
Derivative, notional amount			$ 6.0