OTHER COMPREHENSIVE LOSS - Change in Accumulated Other Comprehensive Loss by Component (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	$ 6,764
Ending balance	55,455	$ 6,764
Pension And Postretirement Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	0	0	$ 0
Other comprehensive (loss) income	(270)	0	0
Ending balance	(270)	0	0
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] | Debt Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	6,764	(40,415)	(20,609)
Other comprehensive (loss) income	48,961	47,179	(19,806)
Ending balance	55,725	6,764	(40,415)
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] | Equity Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	0	0	(6)
Other comprehensive (loss) income	0	0	0
Amounts reclassified from accumulated comprehensive loss per ASU 2016-01	0	0	6
Ending balance	$ 0	$ 0	$ 0