Business Segment's Contribution to Select Statements of Income (Loss) Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Segment Reporting Information [Line Items]
Policy charge revenue	$ 37,369,000	$ 37,860,000	$ 74,845,000	$ 74,899,000
Net investment income	26,417,000	27,614,000	54,361,000	54,066,000
Net realized investment gains (losses)	2,184,000	57,000	2,215,000	(77,000)
Derivative gains (losses)	(6,540,000)	(6,665,000)	(30,768,000)	(3,294,000)
Total Revenues	59,430,000	58,866,000	100,653,000	125,594,000
Interest credited to policyholder liabilities	13,370,000	13,953,000	26,353,000	27,983,000
Policy benefits (net of reinsurance recoveries)	11,889,000	21,859,000	2,399,000	64,913,000
Amortization (accretion) of DAC	605,000	(500,000)	1,737,000	442,000
Amortization (accretion) of VOBA	2,854,000	7,611,000	5,218,000	12,991,000
Insurance, general and administrative expenses	6,577,000	10,242,000	15,420,000	20,168,000
Total Benefits and Expenses	35,295,000	53,165,000	51,127,000	126,497,000
Income (Loss) Before Taxes	24,135,000	5,701,000	49,526,000	(903,000)
Income Tax Expense (Benefit)	0	0	575,000	0
Net Income (Loss)	24,135,000	5,701,000	48,951,000	(903,000)
Operating Segments | Annuity
Segment Reporting Information [Line Items]
Policy charge revenue	23,939,000	24,192,000	47,950,000	47,913,000
Net investment income	13,023,000	13,486,000	27,253,000	25,503,000
Net realized investment gains (losses)	1,887,000	1,052,000	1,689,000	831,000
Derivative gains (losses)	(6,540,000)	(6,670,000)	(30,768,000)	(3,315,000)
Total Revenues	32,309,000	32,060,000	46,124,000	70,932,000
Interest credited to policyholder liabilities	1,847,000	2,255,000	3,533,000	4,426,000
Policy benefits (net of reinsurance recoveries)	3,941,000	12,902,000	(12,180,000)	41,555,000
Amortization (accretion) of DAC	605,000	(500,000)	1,737,000	442,000
Amortization (accretion) of VOBA	612,000	1,356,000	2,235,000	3,089,000
Insurance, general and administrative expenses	5,773,000	9,250,000	13,896,000	18,407,000
Total Benefits and Expenses	12,778,000	25,263,000	9,221,000	67,919,000
Income (Loss) Before Taxes	19,531,000	6,797,000	36,903,000	3,013,000
Income Tax Expense (Benefit)	0	1,324,000	393,000	2,601,000
Net Income (Loss)	19,531,000	5,473,000	36,510,000	412,000
Operating Segments | Life Insurance
Segment Reporting Information [Line Items]
Policy charge revenue	13,430,000	13,668,000	26,895,000	26,986,000
Net investment income	13,394,000	14,128,000	27,108,000	28,563,000
Net realized investment gains (losses)	297,000	(995,000)	526,000	(908,000)
Derivative gains (losses)	0	5,000	0	21,000
Total Revenues	27,121,000	26,806,000	54,529,000	54,662,000
Interest credited to policyholder liabilities	11,523,000	11,698,000	22,820,000	23,557,000
Policy benefits (net of reinsurance recoveries)	7,948,000	8,957,000	14,579,000	23,358,000
Amortization (accretion) of DAC	0	0	0	0
Amortization (accretion) of VOBA	2,242,000	6,255,000	2,983,000	9,902,000
Insurance, general and administrative expenses	804,000	992,000	1,524,000	1,761,000
Total Benefits and Expenses	22,517,000	27,902,000	41,906,000	58,578,000
Income (Loss) Before Taxes	4,604,000	(1,096,000)	12,623,000	(3,916,000)
Income Tax Expense (Benefit)	0	(1,324,000)	182,000	(2,601,000)
Net Income (Loss)	$ 4,604,000	$ 228,000	$ 12,441,000	$ (1,315,000)