Securities (Other securities) (Narrative) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Investment [Line Items]
Fair value of securities pledged	$ 758.1	$ 810.6
FHLB	$ 14.0	$ 14.4
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises
Investment [Line Items]
Percentage of mortgage-backed securities issued by government-sponsored enterprises	74.00%

Percentage of Heartland's Mortgage-backed Securities, Issued by US Government Sponsored Enterprises

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- Definition

Line items represent reporting concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 12
-Sentence Column A

+ Details

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- Definition

The fair value of available-for-sale securities that serve as collateral for borrowings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5086-111524

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- Definition

Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 325
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=75031641&loc=d3e63345-112809

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