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Goodwill and Core Deposit Intangibles - Schedule of Core Deposit Intangibles Activity (Details) - USD ($) $ in Thousands |  |  | 12 Months Ended
--- | --- | --- | ---
May 30, 2017 | Aug. 12, 2016 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Finite-lived Intangible Assets [Roll Forward] |  |  |  |  |
Current period amortization |  |  | $ 5,438 | $ 3,427 | $ 3,388
Core Deposits Intangibles |  |  |  |  |
Finite-lived Intangible Assets [Roll Forward] |  |  |  |  |
CDI, net, beginning of period |  |  | 9,700 | 10,600 | 13,300
Established through acquisitions | $ 48,000 | $ 2,500 |  |  | 700
Reductions due to sale of accounts |  |  | (3,200) | 0 | 0
Current period amortization |  |  | 5,400 | 3,400 | 3,400
Total CDI, net, at end of period |  |  | $ 49,100 | $ 9,700 | $ 10,600

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- Definition Finite-Lived Intangible Assets, Increase (Decrease) From Sale Of Accounts + References No definition available. + Details
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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://www.xbrl.org/2003/role/presentationRef -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 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -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 + Details
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- Definition Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275 + Details
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