Fair Value - Assets and liabilities measured at fair value on a recurring basis - (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Assets
Derivative financial instruments	$ 7,700
Securities available for sale	1,577,999	$ 1,340,427	$ 1,648,193
Liabilities
Derivative financial instruments	7,900
Government-sponsored entities debt
Assets
Securities available for sale	47,613	75,952	85,509
State and municipal obligations
Assets
Securities available for sale	223,816	193,294	220,437
Corporate securities
Assets
Securities available for sale		2,584	1,560
Significant Unobservable Inputs (Level 3)
Assets
Mortgage servicing rights	35,107	29,930	31,119
Changes in fair value of assets
Changes in hierarchy classifications of Level 3 liabilities	0
Recurring basis
Assets
Derivative financial instruments	8,848	1,956	3,306
Loans held for sale	36,968	65,995	70,890
Securities available for sale	1,577,999	1,340,427	1,648,193
Mortgage servicing rights	35,107	29,930	31,119
Fair value of Assets, Total	1,658,922	1,438,308	1,753,508
Liabilities
Derivative financial instruments	8,097	592	3,248
Recurring basis \| Government-sponsored entities debt
Assets
Securities available for sale	47,613	75,952	85,509
Recurring basis \| State and municipal obligations
Assets
Securities available for sale	223,816	193,294	220,437
Recurring basis \| Mortgage-backed securities
Assets
Securities available for sale	1,306,570	1,068,597	1,340,687
Recurring basis \| Corporate securities
Assets
Securities available for sale		2,584	1,560
Recurring basis \| Quoted Prices In Active Markets for Identical Assets (Level 1)
Assets
Securities available for sale		2,584
Fair value of Assets, Total		2,584
Recurring basis \| Quoted Prices In Active Markets for Identical Assets (Level 1) \| Corporate securities
Assets
Securities available for sale		2,584
Recurring basis \| Significant Other Observable Inputs (Level 2)
Assets
Derivative financial instruments	8,848	1,956	3,306
Loans held for sale	36,968	65,995	70,890
Securities available for sale	1,577,999	1,337,843	1,648,193
Fair value of Assets, Total	1,623,815	1,405,794	1,722,389
Liabilities
Derivative financial instruments	8,097	592	3,248
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Government-sponsored entities debt
Assets
Securities available for sale	47,613	75,952	85,509
Recurring basis \| Significant Other Observable Inputs (Level 2) \| State and municipal obligations
Assets
Securities available for sale	223,816	193,294	220,437
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Mortgage-backed securities
Assets
Securities available for sale	1,306,570	1,068,597	1,340,687
Recurring basis \| Significant Other Observable Inputs (Level 2) \| Corporate securities
Assets
Securities available for sale			1,560
Recurring basis \| Significant Unobservable Inputs (Level 3)
Assets
Mortgage servicing rights	35,107	29,930	31,119
Fair value of Assets, Total	35,107	29,930	$ 31,119
Changes in fair value of assets
Fair value of assets at the beginning of the period	31,119	29,037
Servicing assets that resulted from transfers of financial assets	3,112	3,096
Changes in fair value assets due to valuation inputs or assumptions	2,945	(371)
Changes in fair value assets due to increased principal paydowns	2,069	1,832
Fair value of assets at the end of the period	35,107	29,930
Unrealized losses included in accumulated other comprehensive income related to Level 3 financial assets and liabilities	$ 0	$ 0

Represents the amount of servicing assets that resulted from transfers of financial assets.

No definition available.

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- Definition

The element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, the element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. The item represents residential mortgage servicing rights as presented on the statement of financial position which are due to the entity as of the balance sheet date.

+ References

No definition available.

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- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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- References

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- Definition

Amount of debt securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

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- Definition

Amount of gain (loss) recognized in the income statement for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

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-Publisher FASB
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- Definition

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Section 50
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- Definition

Amount of gain (loss) recognized in other comprehensive income, arising from assets, liabilities and financial instruments classified in shareholders' equity measured at fair value on a recurring basis using unobservable inputs (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Amount of transfers of financial instrument classified as a liability into (out of) level 3 of the fair value hierarchy.

+ References

No definition available.

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- Definition

Fair value as of the balance sheet date of interest rate derivative assets, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13433-108611

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- Definition

Fair value as of the balance sheet date of interest rate derivative liabilities, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as liabilities.

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- Definition

Fair value portion of loans held-for-sale including, but not limited to, mortgage loans and finance receivables.

+ References

No definition available.

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