Derivative Financial Instruments (Cash flow hedges) (Narrative) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($) transaction
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Change in net unrealized losses on cash flow hedges	$ 197
Estimated amount to be reclassified from accumulated other comprehensive income to interest expense within the next twelve months	$ 789
Interest Rate Swap | Cash Flow Hedges
Derivative [Line Items]
Number of swap transactions | transaction	5
Derivative, notional amount	$ 85,000
Interest Rate Swap | Cash Flow Hedges | Heartland Financial Statutory Trust IV, V and VII
Derivative [Line Items]
Derivative, notional amount	65,000
Interest Rate Swap | Cash Flow Hedges | Morrill Statutory Trust I and II
Derivative [Line Items]
Derivative, notional amount	$ 20,000