INCOME TAXES- Reconciliations of Income tax expenses (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation [Abstract]
Computed income tax at statutory rate	$ 43,621	$ 89,764	$ 74,349
Federal and state taxes	4,944	4,467	3,768
Benefit of net exempt income	(26,780)	(24,811)	(22,782)
Disallowed NOL carryforward resulting from net exempt income	9,054	15,887	14,904
Deferred tax valuation allowance	(12,095)	(14,108)	(90,521)
Adjustments in net deferred tax assets due to changes in enacted tax rates	0	0	15,402
Share based compensation windfull	157	(1,165)	(1,595)
Non deductible expenses and other permanent differences	(387)	(1,712)	(839)
Tax return to provision adjustments	597	1,846	4
Other-net	(5,061)	1,827	(3,660)
Total income tax expense (benefit)	$ 14,050	$ 71,995	$ (10,970)
Federal and state taxes %	4.20%	1.60%	2.00%
Benefit of net exempt income %	(23.00%)	(10.40%)	(12.00%)
Disallowed NOL carryforward resulting from net exempt income %	7.80%	6.60%	7.80%
Deferred tax valuation allowance %	(10.40%)	(5.90%)	(47.50%)
Adjustments in net deferred tax assets due to changes in enacted tax rates %	0.00%	0.00%	8.10%
Share based compensation windfall %	0.10%	(0.50%)	(0.80%)
Nondeductible expenses and other permanent differences %	(0.30%)	(0.70%)	(0.40%)
Tax-return provision adjustments %	0.50%	0.80%	0.00%
Other-net %	(4.30%)	1.10%	(1.90%)
Computed income tax at statutory tax rate %	37.50%	37.50%	39.00%
Total income tax expense (benefit) %	12.10%	30.10%	(5.70%)