Fair Value Measurements (Narrative) (Detail)	12 Months Ended
	Dec. 31, 2015 USD ($) Year	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Fair Value Measurements Of Financial Instruments [Line Items]
GLB - Lapse rate - lower range	1.00%
GLB - Lapse rate - upper range	6.00%
GLB - Spike lapse rate - lower range	10.00%
GLB - Spike lapse rate - upper range	30.00%
GLB - Ultimate lapse rate	10.00%
GLB - Length of ultimate lapse rate period, years | Year	2
GLB - Adjustment factor for valuable guarantees - lower	10.00%
GLB - Adjustment factor for valuable guarantees - upper	75.00%
Level 1 To Level 2 Transfers	$ 0	$ 189,000,000	$ 19,000,000
Level 2 To Level 1 Transfers	0	0	$ 0
Realized Gain Losses As A Result of Annuitization Changes (GLB)	80,000,000
Realized Gain Losses As A Result of Change in Lapse Assumption (GLB)	(10,000,000)
Realized Gain Losses As A Result of Change in Partial Withdrawal Assumption	110,000,000
Realized Gain Losses As A Result of Valuation Model Refinement (GLB)	$ (45,000,000)
Document Period End Date	Dec. 31, 2015
Assets measured using NAV	$ 2,477,000,000	2,561,000,000
Other Investments [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Assets measured using NAV	25,000,000
Investment Funds Limited Partnerships Partially Owned Investment Companies Fair Value [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Assets measured using NAV	$ 2,477,000,000	$ 2,561,000,000
Redemption Notice Periods Lower Range [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Notice period for redemption for alternative investments investment funds, days	5 days
Redemption Notice Periods Upper Range [Member]
Fair Value Measurements Of Financial Instruments [Line Items]
Notice period for redemption for alternative investments investment funds, days	120 days