Cash Flow Information - Supplemental Information on Cash Flows and Noncash Transactions (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Supplemental cash flow information:
Interest paid	$ 6,198	$ 14,494	$ 29,882
Federal income taxes paid	39,528	44,381	30,726
Schedule of noncash investing and financing activities:
Assets acquired through foreclosure	2,711	164	1,463
Investment securities purchased but not settled	0	14,641	0
Restricted stock granted to officers and directors	1,316	672	1,782
Tb And T Bacshares Inc [Member]
Schedule of noncash investing and financing activities:
Stock issued in acquisition	$ 0	$ 220,273	$ 0