Cost and Market Value Associated with Assets Held in Merchandise Trusts (Detail) - Variable Interest Entity, Primary Beneficiary - Merchandise Trusts - USD ($) $ in Thousands		Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Cost		$ 501,519	$ 489,361
Gross Unrealized Gains		11,830	1,307
Gross Unrealized Losses		(18,753)	(25,992)
Fair Value		494,596	464,676
Short-term investments | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cost		28,567	35,150
Fair Value		28,567	35,150
Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
Cost		9,110	19,170
Gross Unrealized Gains		178	25
Gross Unrealized Losses		(493)	(556)
Fair Value		8,795	18,639
Fixed maturities | U.S. governmental securities | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cost		96	98
Gross Unrealized Gains		9	6
Gross Unrealized Losses			(3)
Fair Value		105	101
Fixed maturities | Corporate debt securities | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cost		8,854	11,922
Gross Unrealized Gains		169	8
Gross Unrealized Losses		(493)	(546)
Fair Value		8,530	11,384
Fixed maturities | Other debt securities | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cost		160	7,150
Gross Unrealized Gains			11
Gross Unrealized Losses			(7)
Fair Value		160	7,154
Mutual funds-debt securities | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cost		245,134	232,096
Gross Unrealized Gains		3,267	86
Gross Unrealized Losses		(6,829)	(10,713)
Fair Value		241,572	221,469
Mutual funds-equity securities | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cost		137,408	139,341
Gross Unrealized Gains		5,502	69
Gross Unrealized Losses		(8,085)	(12,249)
Fair Value		134,825	127,161
Other investment funds
Schedule of Available-for-sale Securities [Line Items]
Cost	[1]	27,458
Gross Unrealized Gains	[1]	183
Fair Value	[1]	27,641
Equity securities | Level 1
Schedule of Available-for-sale Securities [Line Items]
Cost		40,616	49,563
Gross Unrealized Gains		2,386	1,127
Gross Unrealized Losses		(3,346)	(2,474)
Fair Value		39,656	48,216
Other invested assets | Level 2
Schedule of Available-for-sale Securities [Line Items]
Cost		1,630	1,681
Gross Unrealized Gains		314
Fair Value		1,944	1,681
Total managed investments
Schedule of Available-for-sale Securities [Line Items]
Cost		489,923	477,001
Gross Unrealized Gains		11,830	1,307
Gross Unrealized Losses		(18,753)	(25,992)
Fair Value		483,000	452,316
Assets acquired via acquisition
Schedule of Available-for-sale Securities [Line Items]
Cost		3,264	4,185
Fair Value		3,264	4,185
West Virginia Trust Receivable
Schedule of Available-for-sale Securities [Line Items]
Cost		8,332	8,175
Fair Value		$ 8,332	$ 8,175

[1] Other investment funds are measured at fair value using the net asset value per share practical expedient and have not been categorized in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the balance sheet. This asset class is composed of fixed income funds and equity funds which have redemption periods ranging from 30 to 90 days.