MERCHANDISE TRUSTS - Cost and Market Value Associated with Assets Held in Merchandise Trusts (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
West Virginia Trust Receivable
Schedule Of Available For Sale Securities [Line Items]
Fair Value	$ 8,600	$ 9,700
Variable Interest Entity, Primary Beneficiary | Merchandise Trusts
Schedule Of Available For Sale Securities [Line Items]
Cost	509,066	515,680
Gross Unrealized Gains	13,681	11,346
Gross Unrealized Losses	(64,982)	(3,161)
Fair Value	457,765	523,865
Cost, Assets held for sale	(21,778)	(6,369)
Gross Unrealized Gains, Assets held for sale	(425)	(304)
Gross Unrealized Losses,Assets held for sale	2,076
Fair Value, Assets held for sale	(20,127)	(6,673)
Cost, Excluding assets held for sale	487,288	509,311
Gross Unrealized Gains, Excluding assets held for sale	13,256	11,042
Gross Unrealized Losses, Excluding assets held for sale	(62,906)	(3,161)
Fair Value, Excluding assets held for sale	437,638	517,192
Variable Interest Entity, Primary Beneficiary | Short-term investments | Merchandise Trusts | Level 1
Schedule Of Available For Sale Securities [Line Items]
Cost	120,171	144,610
Fair Value	120,171	144,610
Variable Interest Entity, Primary Beneficiary | Fixed maturities | Merchandise Trusts
Schedule Of Available For Sale Securities [Line Items]
Cost	6,767	1,239
Gross Unrealized Gains	27	20
Gross Unrealized Losses	(316)	(198)
Fair Value	6,478	1,061
Variable Interest Entity, Primary Beneficiary | Fixed maturities | Merchandise Trusts | U.S. governmental securities | Level 2
Schedule Of Available For Sale Securities [Line Items]
Cost	474	456
Gross Unrealized Gains	23	6
Gross Unrealized Losses	(82)	(65)
Fair Value	415	397
Variable Interest Entity, Primary Beneficiary | Fixed maturities | Merchandise Trusts | Corporate debt securities | Level 2
Schedule Of Available For Sale Securities [Line Items]
Cost	6,293	783
Gross Unrealized Gains	4	14
Gross Unrealized Losses	(234)	(133)
Fair Value	6,063	664
Variable Interest Entity, Primary Beneficiary | Mutual funds - debt securities | Merchandise Trusts | Level 1
Schedule Of Available For Sale Securities [Line Items]
Cost	30,138	67,801
Gross Unrealized Gains	160	1,857
Gross Unrealized Losses	(2,464)	(6)
Fair Value	27,834	69,652
Variable Interest Entity, Primary Beneficiary | Mutual funds - equity securities | Merchandise Trusts | Level 1
Schedule Of Available For Sale Securities [Line Items]
Cost	46,279	46,609
Gross Unrealized Gains	1,577	1,744
Gross Unrealized Losses	(25,236)
Fair Value	22,620	48,353
Variable Interest Entity, Primary Beneficiary | Other investment funds | Merchandise Trusts
Schedule Of Available For Sale Securities [Line Items]
Cost	235,150	213,024
Gross Unrealized Gains	10,916	6,366
Gross Unrealized Losses	(15,626)	(2,953)
Fair Value	230,440	216,437
Variable Interest Entity, Primary Beneficiary | Equity securities | Merchandise Trusts | Level 1
Schedule Of Available For Sale Securities [Line Items]
Cost	56,668	24,386
Gross Unrealized Gains	1,001	1,327
Gross Unrealized Losses	(20,331)	(4)
Fair Value	37,338	25,709
Variable Interest Entity, Primary Beneficiary | Other invested assets | Merchandise Trusts | Level 2
Schedule Of Available For Sale Securities [Line Items]
Cost	4,387	8,360
Gross Unrealized Gains		32
Gross Unrealized Losses	(94)
Fair Value	4,293	8,392
Variable Interest Entity, Primary Beneficiary | Total investments | Merchandise Trusts
Schedule Of Available For Sale Securities [Line Items]
Cost	499,560	506,029
Gross Unrealized Gains	13,681	11,346
Gross Unrealized Losses	(64,067)	(3,161)
Fair Value	449,174	514,214
Variable Interest Entity, Primary Beneficiary | West Virginia Trust Receivable | Merchandise Trusts
Schedule Of Available For Sale Securities [Line Items]
Cost	9,506	9,651
Gross Unrealized Losses	(915)
Fair Value	$ 8,591	$ 9,651