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Basis of Presentation and Significant Accounting Policies - Summary of Common Shares Issued and Resultant Value of Total Shareholders' Equity (Detail) shares in Thousands, $ in Thousands | 12 Months Ended
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Dec. 31, 2018 USD ($) shares
Common Shares Issued and Value of Shares Holders' Equity [Line Items] |
Acquisition, Total Shareholders' Equity | $ 406,474
Minnesota-Based Klein Financial, Inc. |
Common Shares Issued and Value of Shares Holders' Equity [Line Items] |
Acquisition, Total Shareholders' Equity | $ 406,474
Minnesota-Based Klein Financial, Inc. | Common Stock |
Common Shares Issued and Value of Shares Holders' Equity [Line Items] |
Acquisition, Shares of Common Stock (in shares) | shares | 22,772
Acquisition, Total Shareholders' Equity | $ 22,772

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