Aging of Unrealized Losses on Investments in Fixed Maturities and Equity Securities Held in Merchandise Trusts (Detail) - Variable Interest Entity, Primary Beneficiary - Merchandise Trusts - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	$ 46,677	$ 211,854
Less than 12 months Unrealized Losses	3,522	20,625
12 Months or more Fair Value	203,740	44,342
12 Months or more Unrealized Losses	15,231	5,367
Total Fair Value	250,417	256,196
Total Unrealized Losses	18,753	25,992
Fixed maturities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	4,385	10,130
Less than 12 months Unrealized Losses	314	418
12 Months or more Fair Value	2,116	1,546
12 Months or more Unrealized Losses	179	138
Total Fair Value	6,501	11,676
Total Unrealized Losses	493	556
Fixed maturities | U.S. governmental securities
Investments, Unrealized Loss Position [Line Items]
12 Months or more Fair Value		33
12 Months or more Unrealized Losses		3
Total Fair Value		33
Total Unrealized Losses		3
Fixed maturities | Corporate debt securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	4,385	7,247
Less than 12 months Unrealized Losses	314	411
12 Months or more Fair Value	2,116	1,513
12 Months or more Unrealized Losses	179	135
Total Fair Value	6,501	8,760
Total Unrealized Losses	493	546
Fixed maturities | Other debt securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value		2,883
Less than 12 months Unrealized Losses		7
Total Fair Value		2,883
Total Unrealized Losses		7
Mutual funds-debt securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	16,342	121,777
Less than 12 months Unrealized Losses	463	6,938
12 Months or more Fair Value	138,981	36,682
12 Months or more Unrealized Losses	6,366	3,775
Total Fair Value	155,323	158,459
Total Unrealized Losses	6,829	10,713
Mutual funds-equity securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	11,037	58,467
Less than 12 months Unrealized Losses	899	10,994
12 Months or more Fair Value	55,539	5,465
12 Months or more Unrealized Losses	7,186	1,255
Total Fair Value	66,576	63,932
Total Unrealized Losses	8,085	12,249
Equity securities
Investments, Unrealized Loss Position [Line Items]
Less than 12 months Fair Value	14,913	21,480
Less than 12 months Unrealized Losses	1,846	2,275
12 Months or more Fair Value	7,104	649
12 Months or more Unrealized Losses	1,500	199
Total Fair Value	22,017	22,129
Total Unrealized Losses	$ 3,346	$ 2,474