MERCHANDISE TRUSTS - Additional Information (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2020 USD ($) security	Sep. 30, 2019 USD ($) security	Dec. 31, 2019 USD ($)
West Virginia Trust Receivable
Schedule Of Available For Sale Securities [Line Items]
Trust assets, fair value	$ 9,400		$ 9,700
Merchandise Trusts
Schedule Of Available For Sale Securities [Line Items]
Percentage of VIE for cancellable state	51.50%
Merchandise Trusts | Variable Interest Entity, Primary Beneficiary
Schedule Of Available For Sale Securities [Line Items]
Trust assets, fair value	$ 496,319		523,865
Purchases of available for sale securities	99,800	$ 42,200
Sales, maturities and paydowns of available for sale securities	318,100	30,700
Other than temporary impairments loss	$ 1,655	$ 2,816
Merchandise Trusts | Variable Interest Entity, Primary Beneficiary | Other Than Temporarily Impaired Securities
Schedule Of Available For Sale Securities [Line Items]
Number of securities that incurred other than temporary impairment losses | security	2	87
Trust assets, cost	$ 16,800	$ 96,700
Trust assets, fair value	15,100	93,900
Other than temporary impairments loss	1,700	$ 2,800
Merchandise Trusts | West Virginia Trust Receivable | Variable Interest Entity, Primary Beneficiary
Schedule Of Available For Sale Securities [Line Items]
Trust assets, fair value	$ 9,376		$ 9,651