Fair Value Measurements (Narrative) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014 Year	Dec. 31, 2013	Dec. 31, 2012
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	2
GLB - Adjustment factor for valuable guarantees - lower	10.00%
GLB - Adjustment factor for valuable guarantees - upper	75.00%
Guaranteed Living Benefits, Net Income Impact From Model Refinement	$ 2,000,000	$ 9,000,000	$ 49,000,000
Level 1 To Level 2 Transfers	189,000,000	19,000,000	40,000,000
Level 2 To Level 1 Transfers	0	0	15,000,000
Realized Gain Losses As A Result of Annuitization Changes (GLB)	39,000,000
Realized Gain Losses As A Result of Change in Lapse Assumption (GLB)	31,000,000
Realized Gain Losses As A Result of Valuation Model Refinement (GLB)	$ (78,000,000)
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