Cash Flow Information - Supplemental Information on Cash Flows and Noncash Transactions (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental cash flow information:
Interest paid	$ 18,709	$ 9,316	$ 5,465
Federal income taxes paid	26,578	29,695	28,348
Schedule of noncash investing and financing activities:
Assets acquired through foreclosure	126	2,211	2,269
Investment securities purchased but not settled			12,381
Restricted stock grant to officers and directors	$ 1,609	$ 1,139	$ 810