Fair Value Measurement - Summary of Quantitative Information About Level 3 Fair Value Measurements (Details) - Level 3 [Member] $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Quantitative Information About Level 3 Fair Value Measurements [Abstract]
Fair Value	$ 537,655	$ 537,072
Fair Value on a Nonrecurring Basis [Member]
Quantitative Information About Level 3 Fair Value Measurements [Abstract]
Fair Value	3,587	3,794
Fair Value on a Nonrecurring Basis [Member] \| Impaired Loans [Member] \| Appraised Values [Member]
Quantitative Information About Level 3 Fair Value Measurements [Abstract]
Fair Value	$ 2,231	$ 2,438
Unobservable Input	Age of appraisal, current market conditions, experience within local market	Age of appraisal, current market conditions, experience within local market
Fair Value on a Nonrecurring Basis [Member] \| Impaired Loans [Member] \| Appraised Values [Member] \| Weighted Average [Member]
Quantitative Information About Level 3 Fair Value Measurements [Abstract]
Weighted Average Discount	0.83	0.86
Fair Value on a Nonrecurring Basis [Member] \| Other Real Estate Owned [Member] \| Appraised Values [Member]
Quantitative Information About Level 3 Fair Value Measurements [Abstract]
Fair Value	$ 1,356	$ 1,356
Unobservable Input	Age of appraisal, current market conditions and selling costs	Age of appraisal, current market conditions and selling costs
Fair Value on a Nonrecurring Basis [Member] \| Other Real Estate Owned [Member] \| Appraised Values [Member] \| Weighted Average [Member]
Quantitative Information About Level 3 Fair Value Measurements [Abstract]
Weighted Average Discount	0.17	0.18

Value of input used to measure alternative investment.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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- References

No definition available.

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Description of the valuation processes in place for fair value measurements categorized within Level 3 of the fair value hierarchy.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

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