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Goodwill and Other Intangible Assets - Additional Information (Details) - USD ($) $ in Thousands | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Nov. 30, 2019
Goodwill [Line Items] |  |  |  |  |
Goodwill acquired | [1] | $ 84,175 | $ 0 |  |
Goodwill, written off related to sale of business unit |  | 0 | 4,224 |  |
Core deposits and other intangible assets |  | 10,900 |  |  |
Finite-lived intangible assets acquired | [2] | 9,154 | 80 |  |
Amortization expense on finite-lived intangible assets |  | 800 | $ 900 | $ 1,200 |
DNB |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |
Goodwill acquired |  | 84,200 |  |  |
Core Deposits |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |
Finite-lived intangible assets acquired |  | 7,300 |  |  |
Core Deposits | DNB |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |
Core deposits and other intangible assets |  |  |  |  | $ 7,288
Wealth Management |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |
Finite-lived intangible assets acquired |  | $ 1,900 |  |  |
Wealth Management | DNB |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |
Core deposits and other intangible assets |  |  |  |  | $ 1,772
[1] | Management is continuing to evaluate the purchase accounting fair value adjustments for the DNB merger. Any changes in preliminary estimates will be adjusted in goodwill in subsequent periods, but not extending beyond one year from the date of acquisition.
[2] | Management is still evaluating the intangible asset valuation due to the final independent valuation report not being complete. Any changes in preliminary estimates will be adjusted in goodwill in subsequent periods, but not extending beyond one year from the date of acquisition.

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- Definition The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274 + Details
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