Goodwill and Intangible Assets - Summary of Intangible Assets (Details) $ in Thousands	3 Months Ended
Mar. 31, 2019 USD ($)
Finite-lived Intangible Assets [Roll Forward]
Core deposit intangible, net, end of year	$ 31,048
Core deposit
Finite-lived Intangible Assets [Roll Forward]
Gross core deposit intangible balance, beginning of period	20,574
Additions	23,333
Gross core deposit intangible, end of period	43,907
Accumulated amortization	(12,859)
Core deposit intangible, net, end of year	$ 31,048

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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

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- Definition

Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

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- Definition

Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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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.

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- Definition

Amount of increase in assets, excluding financial assets, lacking physical substance with a definite life, from an acquisition.

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