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
	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