Summary of Changes in Fair Value of Level 3 Liabilities (Assets) (Detail) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Mar. 31, 2017	Dec. 31, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities, balance at beginning of period		$ 55,143
Liabilities, balance at end of period		48,395	$ 55,143
Assets, Balance at beginning of period		(57,381)
Assets, balance at end of period		(52,532)	(57,381)
GMWB
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities, balance at beginning of period	[1]	54,414	60,618
Liabilities, balance at end of period	[1]	47,666	54,414
GMWB | Interest rates
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities, gain (loss) included in earnings	[2]	1,532	(4,179)
GMWB | Equity markets
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities, gain (loss) included in earnings	[2]	(7,963)	(5,988)
GMWB | Other
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities, gain (loss) included in earnings	[2]	(317)	3,963
GMIB
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets, Balance at beginning of period	[1]	(48,166)	(61,426)
Assets, balance at end of period	[1]	(39,244)	(48,166)
GMIB | Interest rates
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets, gain (loss) included in earnings	[2]	(802)	2,262
GMIB | Equity markets
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets, gain (loss) included in earnings	[2]	9,199	12,560
GMIB | Other
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets, gain (loss) included in earnings	[2]	525	(1,562)
SALB
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities, balance at beginning of period	[1]	729	511
Liabilities, balance at end of period	[1]	$ 729	729
SALB | Equity markets
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities, gain (loss) included in earnings	[2]		$ 218

[1] GMWB and SALB are recorded as a component of future policy benefits on the Balance Sheets and GMIB reinsurance is recorded as recoverable of ceded GMIB embedded derivatives, at fair value on the Balance Sheets.

[2] Recorded as a component of policy benefits in the Statements of Income (Loss).