PARENT COMPANY FINANCIAL INFORMATION (Statements of Income) (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income:
Other income									$ 7,104	$ 5,642	$ 4,916
Expenses:
Total interest expense	$ 19,807	$ 20,292	$ 21,029	$ 21,433	$ 19,462	$ 16,783	$ 14,779	$ 12,613	82,561	63,637	26,031
Income before income taxes and equity in undistributed income of of subsidiary	37,071	38,914	37,221	39,655	34,105	38,341	31,871	28,371	152,861	132,688	87,935
Income Tax Expense (Benefit)	(8,614)	(9,531)	(8,945)	(9,338)	(8,539)	(9,107)	(7,472)	(6,706)	(36,428)	(31,824)	(34,726)
Net income	$ 28,457	$ 29,383	$ 28,276	$ 30,317	$ 25,566	$ 29,234	$ 24,399	$ 21,665	116,433	100,864	53,209
Parent Company [Member]
Income:
Cash dividends from subsidiary									42,625	39,370	25,420
Other income									1,093	897	1,832
Total income									43,718	40,267	27,252
Expenses:
Interest									3,141	1,922	12
Other expenses									1,507	1,135	970
Total interest expense									4,648	3,057	982
Income before income taxes and equity in undistributed income of of subsidiary									39,070	37,210	26,270
Income Tax Expense (Benefit)									(734)	(283)	331
Income before equity in undistributed income of subsidiary									39,804	37,493	25,939
Equity in undistributed income of subsidiary									76,629	63,371	27,270
Net income									$ 116,433	$ 100,864	$ 53,209