MERCHANDISE TRUSTS - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) security	Dec. 31, 2019 USD ($) security
West Virginia Trust Receivable
Schedule Of Available For Sale Securities [Line Items]
Trust assets, fair value	$ 10,000	$ 9,700
Merchandise Trusts
Schedule Of Available For Sale Securities [Line Items]
Percentage of VIE for cancellable state	45.40%
Merchandise Trusts | Variable Interest Entity, Primary Beneficiary
Schedule Of Available For Sale Securities [Line Items]
Trust assets, fair value	$ 516,284	523,865
Purchases of available for sale securities	52,900	54,400
Sales, maturities and paydowns of available for sale securities	56,400	38,100
Other than temporary impairments loss	$ 26,714	$ 6,056
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	57	102
Trust assets, cost	$ 106,400	$ 178,200
Trust assets, fair value	79,700	172,200
Other than temporary impairments loss	26,700	6,100
Merchandise Trusts | West Virginia Trust Receivable | Variable Interest Entity, Primary Beneficiary
Schedule Of Available For Sale Securities [Line Items]
Trust assets, fair value	$ 9,969	$ 9,651