Fair Value Measurements - Textual (Details) - USD ($)	6 Months Ended
Jun. 30, 2018	Dec. 31, 2017
Fair Value Measurements (Textual) [Abstract]
Impairment of goodwill	$ 0	$ 0
Core deposit intangible assets
Fair Value Measurements (Textual) [Abstract]
Impairment valuation allowance	$ 0	0
Non-compete intangible assets
Fair Value Measurements (Textual) [Abstract]
Expected life of intangible assets	1 year
Minimum \| Core deposit intangible assets
Fair Value Measurements (Textual) [Abstract]
Expected life of intangible assets	10 years
Maximum \| Core deposit intangible assets
Fair Value Measurements (Textual) [Abstract]
Expected life of intangible assets	15 years
Loans Held For Sale
Fair Value Measurements (Textual) [Abstract]
Loans held for sale that were on nonaccrual status	$ 0	0
Loans held for sale that were 90 days past due and on accrual status	$ 0	0
Total Impaired Loans \| Minimum
Fair Value Measurements (Textual) [Abstract]
Percentage of discount factors used to determine fair value	20.00%
Total Impaired Loans \| Maximum
Fair Value Measurements (Textual) [Abstract]
Percentage of discount factors used to determine fair value	30.00%
Other Real Estate and Repossessed Assets \| Minimum
Fair Value Measurements (Textual) [Abstract]
Percentage of discount factors used to determine fair value	20.00%
Other Real Estate and Repossessed Assets \| Maximum
Fair Value Measurements (Textual) [Abstract]
Percentage of discount factors used to determine fair value	30.00%
Measured on a Recurring Basis
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	$ 2,686,311,000	2,098,201,000
Fair Value Measurements (Textual) [Abstract]
Liabilities recorded at fair value	20,407,000	12,357,000
Measured on a Nonrecurring Basis
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	52,081,000	73,518,000
Fair Value Measurements (Textual) [Abstract]
Liabilities recorded at fair value	0	0
Measured on a Nonrecurring Basis \| Impaired loans
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Assets, fair value disclosure	$ 50,394,000	$ 70,619,000

Fair value measurements.

No definition available.

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Percentage of discount factors used to determine fair value.

+ References

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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)
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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This item represents the aggregate fair value of loans held as assets that are 90 days or more past due for which the fair value option has been elected.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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This item represents the aggregate fair value of loans held as assets that are in nonaccrual status for which the fair value option has been elected, if the entity's policy is to recognize interest income separately from other changes in fair value.

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Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount of accumulated impairment loss for an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
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Fair value of financial and nonfinancial obligations.

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Reflects the estimated amount of impairment as of the balance sheet date of recognized servicing assets that are being amortized in proportion to and over the period of estimated net servicing income or loss.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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