MERCHANDISE TRUSTS - Additional Information (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) security	Jun. 30, 2018 USD ($) security	Dec. 31, 2018 USD ($)
West Virginia Trust Receivable
Schedule Of Available For Sale Securities [Line Items]
Trust assets, fair value	$ 9,300		$ 9,300		$ 8,700
Merchandise Trusts
Schedule Of Available For Sale Securities [Line Items]
Percentage of VIE for cancellable state	53.60%		53.60%
Merchandise Trusts | Variable Interest Entity, Primary Beneficiary
Schedule Of Available For Sale Securities [Line Items]
Trust assets, fair value	$ 519,382		$ 519,382		488,248
Purchases of available for sale securities			29,100	$ 44,500
Sales, maturities and paydowns of available for sale securities			19,900	35,700
Trust assets, cost	504,651		504,651		497,282
Other than temporary impairments loss			2,314	11,154
Merchandise Trusts | Variable Interest Entity, Primary Beneficiary | Other Than Temporarily Impaired Securities
Schedule Of Available For Sale Securities [Line Items]
Trust assets, fair value	89,600	$ 154,600	$ 89,600	$ 154,600
Number of securities that incurred other than temporary impairment losses | security			89	94
Trust assets, cost	91,900	165,800	$ 91,900	$ 165,800
Other than temporary impairments loss	0	$ 0	2,300	$ 11,200
Merchandise Trusts | West Virginia Trust Receivable | Variable Interest Entity, Primary Beneficiary
Schedule Of Available For Sale Securities [Line Items]
Trust assets, fair value	9,322		9,322		8,663
Trust assets, cost	$ 9,322		$ 9,322		$ 8,663