Income Tax Level 4 Deferred tax assets (liabilities) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Deferred Tax Assets, Net of Valuation Allowance [Abstract]
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Policyholder Liabilities	$ 101	$ 119
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Loss Reserves	6	4
Deferred Tax Assets, Gross, Current	32	0
Deferred Tax Assets, Investments	135	524
Deferred Tax Assets, Derivative Instruments	79	90
Deferred Tax Assets, Operating Loss Carryforwards	1,155	1,166
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	232	232
Deferred Tax Assets, Tax Credit Carryforwards, Foreign	40	122
Deferred Tax Assets, Other	191	16
Deferred Tax Assets, Gross	1,971	2,273
Deferred Tax Assets, Net of Valuation Allowance, Current	1,971	2,273
Components of Deferred Tax Liabilities [Abstract]
Deferred Tax Liabilities, Deferred Expense, Deferred Policy Acquisition Cost	0	(220)
Deferred Tax Liabilities Net Unrealized gains on Investments	480	432
Deferred Tax Liabilities, Employee Benefits	54	40
Deferred Tax Liabilities, Net	534	692
Deferred Tax Assets, Net	1,437	1,581
Income Taxes Receivable, Current	$ 64	276
Valuation Allowance, Deferred Tax Asset, Explanation of Change	The Company believes it is more likely than not that all deferred tax assets will be fully realized. In assessing the need for a valuation allowance, management considered future taxable temporary difference reversals, future taxable income exclusive of reversing temporary differences and carryovers, taxable income in open carry back years and other tax planning strategies. From time to time, tax planning strategies could include holding a portion of debt securities with market value losses until recovery, altering the level of tax exempt securities held, making investments which have specific tax characteristics, and business considerations such as asset-liability matching.
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	$ 3,301
Operating Loss Carryforwards		$ 3,333
Expected Tax Benefit Attributable to Net Operating Losses Domestic Near term	$ 3,299
Latest Tax Year [Member]
Components of Deferred Tax Liabilities [Abstract]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2029