Derivative Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Non-hedging derivative financial instruments
Derivative Financial Instruments
Notional or contractual amount	$ 810,072	$ 784,444
Asset derivatives, Fair value	7,472	5,233
Liability derivatives, Fair value	7,527	5,272
Interest rate swap contracts
Derivative Financial Instruments
Asset derivatives, Fair value	7,355	5,194
Interest rate swap contracts \| Non-hedging derivative financial instruments
Derivative Financial Instruments
Notional or contractual amount	789,268	756,550
Asset derivatives, Fair value	7,349	5,167
Liability derivatives, Fair value	7,480	5,262
Loan commitments \| Non-hedging derivative financial instruments
Derivative Financial Instruments
Notional or contractual amount	6,931	8,504
Asset derivatives, Fair value	123	66
Liability derivatives, Fair value	0	0
Forward contracts - mortgage loan \| Non-hedging derivative financial instruments
Derivative Financial Instruments
Notional or contractual amount	13,873	19,390
Asset derivatives, Fair value	0	0
Liability derivatives, Fair value	$ 47	$ 10

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 20
-Section 55
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=99393222&loc=SL20226000-175313

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 20
-Section 50
-Paragraph 4D
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=109247956&loc=SL51823488-111719

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-SubTopic 20
-Section 50
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
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-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (a),(c)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959

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+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 860
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-Section 50
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No definition available.

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