Other Borrowed Funds and Subordinated Debentures - Summary of Other Borrowed Funds and Subordinated Debentures (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
Amount outstanding at December 31	$ 407,038,000	$ 238,461,000	$ 383,861,000
Weighted average rate at December 31	2.37%	2.76%	2.26%
Maximum amount outstanding at any month end	$ 487,502,000	$ 542,913,000	$ 491,583,000
Daily average balance outstanding during the year	$ 231,926,000	$ 291,674,000	$ 309,102,000
Weighted average rate during the year	2.95%	2.61%	2.42%