Summary of Quantitative Inputs and Assumptions of Level 3 Assets and Liabilities (Detail) - USD ($) $ in Thousands		6 Months Ended	12 Months Ended
		Jun. 30, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value Inputs Assets And Liabilities Quantitative Information [Line Items]
Estimated Fair Value		$ 90,970	$ 70,208
Future policy benefits (embedded derivatives), fair value		$ 85,001	$ 61,129
Own credit risk		0.50%	0.40%
Long-term volatility		25.00%	25.00%
Fixed maturity AFS securities
Fair Value Inputs Assets And Liabilities Quantitative Information [Line Items]
Estimated Fair Value	[1]	$ 6,760	$ 6,666	$ 8,474
Fixed maturity AFS securities | Asset-backed securities
Fair Value Inputs Assets And Liabilities Quantitative Information [Line Items]
Estimated Fair Value		3,821	6,666
Fixed maturity AFS securities | Asset-backed securities 2
Fair Value Inputs Assets And Liabilities Quantitative Information [Line Items]
Estimated Fair Value		2,939
Limited partnership
Fair Value Inputs Assets And Liabilities Quantitative Information [Line Items]
Estimated Fair Value	[1]	10,376	2,116	4,086
GMWB
Fair Value Inputs Assets And Liabilities Quantitative Information [Line Items]
Future policy benefits (embedded derivatives), fair value	[2]	84,490	60,618	60,702
GMIB
Fair Value Inputs Assets And Liabilities Quantitative Information [Line Items]
Estimated Fair Value	[2]	73,834	61,426	60,573
SALB
Fair Value Inputs Assets And Liabilities Quantitative Information [Line Items]
Future policy benefits (embedded derivatives), fair value	[2]	$ 511	$ 511	$ 504
Level 3 | Fixed maturity AFS securities | Asset-backed securities
Fair Value Inputs Assets And Liabilities Quantitative Information [Line Items]
Valuation Technique		Broker
Level 3 | Fixed maturity AFS securities | Asset-backed securities 2
Fair Value Inputs Assets And Liabilities Quantitative Information [Line Items]
Valuation Technique		Recent Purchase Price
Level 3 | Limited partnership
Fair Value Inputs Assets And Liabilities Quantitative Information [Line Items]
Valuation Technique	[3]	Not applicable
Level 3 | GMWB
Fair Value Inputs Assets And Liabilities Quantitative Information [Line Items]
Valuation Technique		Discounted cash flows
Level 3 | GMWB | Weighted Average
Fair Value Inputs Assets And Liabilities Quantitative Information [Line Items]
Own credit risk		0.50%	0.40%
Long-term volatility		25.00%
Long-term volatility			25.00%
Long-term volatility		30.00%
Level 3 | GMIB
Fair Value Inputs Assets And Liabilities Quantitative Information [Line Items]
Valuation Technique		Discounted cash flows
Level 3 | GMIB | Weighted Average
Fair Value Inputs Assets And Liabilities Quantitative Information [Line Items]
Own credit risk		0.50%	0.40%
Long-term volatility		25.00%
Long-term volatility			25.00%
Long-term volatility		30.00%

[1] Recorded as a component of limited partnerships and fixed maturity AFS securities in the Balance Sheets.

[2] 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.

[3] The Company has obtained non-binding broker quotes which cannot be corroborated by market observable data, to assist in determining the fair values of the Level 3 asset-backed securities. The Company does not receive the unobservable inputs used by the broker but performs annual reviews to approve the use of brokers and obtains an asset specialist's review of the broker's price.