Fair Value Measurements (Narrative) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) Year	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
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	11.00%
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	$ 167
Realized Gain Losses As A Result of Change in Lapse Assumption (GLB)	4
Realized Gain Losses As A Result of Annuitization Changes (GLB)	221
Realized Gain Losses As A Result of Valuation Model Refinement (GLB)	23
Fair Value, Level 1 to Level 2 transfers, Amount	189
Assets measured using NAV	3,627	$ 2,477
Other investments	$ 4,519	3,291
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	$ 25	25
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	3,626	2,477
Guaranteed Minimum Income Benefit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
GLB liability	$ 853	$ 888	$ 663	$ 427