Shareholders' Equity - Components of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning, balance	$ 280	$ 339	$ 678
Other comprehensive income (loss) before reclassifications, after tax	(795)	(28)	(368)
Reclassification of (gains) losses from accumulated other comprehensive income, after tax	77	(41)	(10)
Other comprehensive loss	(718)	(69)	(378)
Issuance of equity securities by subsidiary	1		2
Amounts attributable to noncontrolling interests	80	10	37
Ending, balance	(357)	280	339
OTTI Gains (Losses) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning, balance	32	23	18
Sale of subsidiaries		(5)
Other comprehensive income (loss) before reclassifications, after tax	(23)	15	6
Reclassification of (gains) losses from accumulated other comprehensive income, after tax	14
Other comprehensive loss	(9)	15	6
Amounts attributable to noncontrolling interests	1	(1)	(1)
Ending, balance	24	32	23
Unrealized Gains (Losses) on Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning, balance	846	622	1,233
Sale of subsidiaries		(15)
Other comprehensive income (loss) before reclassifications, after tax	(600)	295	(658)
Reclassification of (gains) losses from accumulated other comprehensive income, after tax	43	(28)	(21)
Other comprehensive loss	(557)	267	(679)
Amounts attributable to noncontrolling interests	58	(28)	68
Ending, balance	347	846	622
Discontinued Operations [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning, balance		(3)	20
Sale of subsidiaries		20
Other comprehensive income (loss) before reclassifications, after tax		2	(6)
Reclassification of (gains) losses from accumulated other comprehensive income, after tax		(21)	(17)
Other comprehensive loss		(19)	(23)
Amounts attributable to noncontrolling interests		2
Ending, balance			(3)
Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning, balance	(6)	(4)	(4)
Other comprehensive income (loss) before reclassifications, after tax	(2)	(2)	(6)
Reclassification of (gains) losses from accumulated other comprehensive income, after tax	7	(1)	6
Other comprehensive loss	5	(3)
Amounts attributable to noncontrolling interests	(2)	1
Ending, balance	(3)	(6)	(4)
Pension Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning, balance	(641)	(432)	(732)
Other comprehensive income (loss) before reclassifications, after tax	(31)	(244)	307
Reclassification of (gains) losses from accumulated other comprehensive income, after tax	13	9	22
Other comprehensive loss	(18)	(235)	329
Issuance of equity securities by subsidiary	1		2
Amounts attributable to noncontrolling interests	9	26	(31)
Ending, balance	(649)	(641)	(432)
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning, balance	49	133	143
Other comprehensive income (loss) before reclassifications, after tax	(139)	(94)	(11)
Other comprehensive loss	(139)	(94)	(11)
Amounts attributable to noncontrolling interests	14	10	1
Ending, balance	$ (76)	$ 49	$ 133