Summary of Changes in Fair Value of Level 3 Liabilities (Assets) (Detail) - USD ($) $ in Thousands		6 Months Ended	12 Months Ended
		Jun. 30, 2016	Dec. 31, 2015
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities, balance at beginning of period		$ 61,129
Liabilities, balance at end of period		85,001	$ 61,129
Assets, Balance at beginning of period		(70,208)
Assets, balance at end of period		(90,970)	(70,208)
GMIB
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets, Balance at beginning of period	[1]	(61,426)	(60,573)
Assets, balance at end of period	[1]	(73,834)	(61,426)
GMIB | Interest rates
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets, gain (loss) included in earnings	[2]	(13,069)	979
GMIB | Equity markets
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets, gain (loss) included in earnings	[2]	808	(1,976)
GMIB | Other
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets, gain (loss) included in earnings	[2]	(147)	144
GMWB
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities, balance at beginning of period	[1]	60,618	60,702
Liabilities, balance at end of period	[1]	84,490	60,618
GMWB | Interest rates
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities, gain (loss) included in earnings	[2]	20,657	(1,890)
GMWB | Equity markets
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities, gain (loss) included in earnings	[2]	3,361	9,182
GMWB | Other
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities, gain (loss) included in earnings	[2]	(146)	(7,376)
SALB
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities, balance at beginning of period	[1]	511	504
Liabilities, balance at end of period	[1]	$ 511	511
SALB | Equity markets
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities, gain (loss) included in earnings	[2]		$ 7

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

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