Shareholders' Equity - Components of Accumulated Other Comprehensive Income (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning, balance	$ 339	$ 678	$ 384
Other comprehensive income (loss) before reclassifications, after tax	(28)	(368)	303
Reclassification of (gains) losses from accumulated other comprehensive income, after tax	(41)	(10)	19
Other comprehensive income (loss)	(69)	(378)	322
Issuance of equity securities by subsidiary		2	5
Amounts attributable to noncontrolling interests	10	37	(33)
Ending, balance	280	339	678
OTTI Gains (Losses) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning, balance	23	18	(57)
Sale of subsidiaries	(5)
Other comprehensive income (loss) before reclassifications, after tax	15	6	102
Reclassification of (gains) losses from accumulated other comprehensive income, after tax			(18)
Other comprehensive income (loss)	15	6	84
Amounts attributable to noncontrolling interests	(1)	(1)	(9)
Ending, balance	32	23	18
Unrealized Gains (Losses) on Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning, balance	622	1,233	929
Sale of subsidiaries	(15)
Other comprehensive income (loss) before reclassifications, after tax	295	(658)	281
Reclassification of (gains) losses from accumulated other comprehensive income, after tax	(28)	(21)	58
Other comprehensive income (loss)	267	(679)	339
Amounts attributable to noncontrolling interests	(28)	68	(35)
Ending, balance	846	622	1,233
Discontinued Operations [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning, balance	(3)	20	31
Sale of subsidiaries	20
Other comprehensive income (loss) before reclassifications, after tax	2	(6)	28
Reclassification of (gains) losses from accumulated other comprehensive income, after tax	(21)	(17)	(39)
Other comprehensive income (loss)	(19)	(23)	(11)
Amounts attributable to noncontrolling interests	2
Ending, balance		(3)	20
Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning, balance	(4)	(4)	(6)
Other comprehensive income (loss) before reclassifications, after tax	(2)	(6)	(2)
Reclassification of (gains) losses from accumulated other comprehensive income, after tax	(1)	6	5
Other comprehensive income (loss)	(3)		3
Amounts attributable to noncontrolling interests	1		(1)
Ending, balance	(6)	(4)	(4)
Pension Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning, balance	(432)	(732)	(621)
Other comprehensive income (loss) before reclassifications, after tax	(244)	307	(145)
Reclassification of (gains) losses from accumulated other comprehensive income, after tax	9	22	13
Other comprehensive income (loss)	(235)	329	(132)
Issuance of equity securities by subsidiary		2	5
Amounts attributable to noncontrolling interests	26	(31)	16
Ending, balance	(641)	(432)	(732)
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning, balance	133	143	108
Other comprehensive income (loss) before reclassifications, after tax	(94)	(11)	39
Other comprehensive income (loss)	(94)	(11)	39
Amounts attributable to noncontrolling interests	10	1	(4)
Ending, balance	$ 49	$ 133	$ 143