MERCHANDISE TRUSTS - Additional Information (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($) Security	Sep. 30, 2020 USD ($) Security	Dec. 31, 2020 USD ($)
West Virginia Trust Receivable
Schedule Of Available For Sale Securities [Line Items]
Trust assets, fair value	$ 10,300		$ 10,000
Merchandise Trusts
Schedule Of Available For Sale Securities [Line Items]
Percentage of VIE for cancellable state	47.90%
Merchandise Trusts | Variable Interest Entity, Primary Beneficiary
Schedule Of Available For Sale Securities [Line Items]
Trust assets, fair value	$ 548,541		516,284
Purchases of available for sale securities	62,300	$ 99,800
Sales, maturities and paydowns of available for sale securities	37,800	318,100
Other than temporary impairments loss	$ 136	$ 1,655
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	6	2
Trust assets, cost	$ 300	$ 16,800
Trust assets, fair value	200	15,100
Other than temporary impairments loss	100	$ 1,700
Merchandise Trusts | West Virginia Trust Receivable | Variable Interest Entity, Primary Beneficiary
Schedule Of Available For Sale Securities [Line Items]
Trust assets, fair value	$ 10,265		$ 9,969