Derivatives and Hedging Activities - Pre-tax Gains and Losses on Derivative Contracts (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Amount of loss recognized in other comprehensive income (effective portion)		$ 1.1	$ 0.2
Designated as Hedging Instrument
Derivative [Line Items]
Amount of loss recognized in other comprehensive income (effective portion)	$ 0.0	1.1	0.2
Reclassification adjustment for derivative net (gains) losses included in income	0.0	1.1	0.0
Not Designated as Hedging Instrument \| Interest Rate Swap
Derivative [Line Items]
Amount of gain (loss) recognized in other non-interest income	0.3	0.0	0.1
Amount of net fee income recognized in other non-interest income	1.3	0.8	0.9
Amount of net gains (losses) recognized in mortgage banking revenues	$ (0.5)	$ (1.7)	$ 1.4

Amount of net gains (losses) included in mortgage banking revenues

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- Definition

Fee Income on Derivatives

+ References

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- Definition

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5618551-113959

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- Definition

The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References

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- Definition

Line items represent financial 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

No definition available.

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- Definition

Amount before tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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