Fair Value Measurements (Narrative) (Detail)		12 Months Ended
		Dec. 31, 2017 USD ($) Year	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
GLB - Lapse rate - lower range		3.00%
GLB - Lapse rate - upper range		9.00%
GLB - Spike lapse rate - lower range		6.00%
GLB - Spike lapse rate - upper range		33.00%
GLB - Ultimate lapse rate		10.00%
GLB - Length of ultimate lapse rate period, years | Year		2
GLB - Adjustment factor for valuable guarantees - lower		15.00%
GLB - Adjustment factor for valuable guarantees - upper		75.00%
Realized Gain Losses As A Result of Change in Partial Withdrawal Assumption		$ 43,000,000
Realized Gain Losses As A Result of Change in Lapse Assumption (GLB)		9,000,000
Realized Gain Losses As A Result of Annuitization Changes (GLB)		117,000,000
Realized Gain Losses As A Result of Valuation Model Refinement (GLB)		94,000,000
Fair Value, Level 1 to Level 2 transfers, Amount		0	$ 0	$ 0
Assets measured using NAV		3,623,000,000	3,627,000,000
Other investments (cost – $4,417 and $4,270)		4,672,000,000	4,519,000,000
Derivative, Gain (Loss) on Derivative, Net		87,000,000	(126,000,000)	(193,000,000)
Guaranteed Minimum Income Benefit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Gain (Loss) on Derivative, Net	[1]	364,000,000	53,000,000	(203,000,000)
Guaranteed Minimum Income Benefit | Variable Annuity [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Gain (Loss) on Derivative, Net	[1]	$ 25,000,000
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notice period for redemption for alternative investments investment funds, days		5 days
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notice period for redemption for alternative investments investment funds, days		120 days
Other Investments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments (cost – $4,417 and $4,270)		$ 15,000,000	25,000,000
Investment Funds Limited Partnerships Partially Owned Investment Companies Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments (cost – $4,417 and $4,270)		3,623,000,000	3,626,000,000
Guaranteed Minimum Income Benefit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
GLB liability		$ 550,000,000	$ 853,000,000	$ 888,000,000	$ 663,000,000

[1] (2) Excludes foreign exchange gains (losses) related to GLB.