Derivative Financial Instruments (Executed interest rate swap) (Details) (Derivative Financial Instruments, USD $) In Millions, unless otherwise specified	Apr. 20, 2011	Mar. 31, 2015 transaction
Derivative [Line Items]
Derivative, notional amount	$ 15.0
Heartland Financial Statutory Trust VI
Derivative [Line Items]
Derivative, notional amount		20.0
Number of swap transactions		2
Cash Flow Hedges
Derivative [Line Items]
Derivative, notional amount		81.2
Number of swap transactions		3
Cash Flow Hedges | Heartland Financial Statutory Trust IV, V and VII
Derivative [Line Items]
Derivative, notional amount		65.0
Cash Flow Hedges | Morrill Statutory Trust I and II
Derivative [Line Items]
Derivative, notional amount		$ 16.2