Net Investment Income (Loss) By Source (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Net Investment Income [Line Items]
Gross investment income	$ 29,166	$ 27,572
Less investment expenses	(1,222)	(1,120)
Net investment income (loss)	27,944	26,452
Limited partnership
Net Investment Income [Line Items]
Gross investment income	1,664	(2,540)
Fixed maturity AFS securities
Net Investment Income [Line Items]
Gross investment income	15,464	17,366
Equity AFS securities
Net Investment Income [Line Items]
Gross investment income	418	465
Mortgage loans on real estate
Net Investment Income [Line Items]
Gross investment income	1,463	1,203
Policy loans
Net Investment Income [Line Items]
Gross investment income	8,220	8,608
Derivatives
Net Investment Income [Line Items]
Gross investment income	1,590	1,912
Cash and Cash Equivalents
Net Investment Income [Line Items]
Gross investment income	274	451
Other
Net Investment Income [Line Items]
Gross investment income	$ 73	$ 107