Shareholders' Equity - Components of Accumulated Other Comprehensive Income (Parenthetical) (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]
Tax on reclassification from accumulated other comprehensive income	$ 457	$ 656	$ 513
OTTI Gains (Losses) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax on change in other comprehensive income (loss) before reclassifications	(8)	(3)	(54)
Tax on reclassification from accumulated other comprehensive income	0	0	10
Unrealized Gains (Losses) on Investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax on change in other comprehensive income (loss) before reclassifications	(132)	354	(151)
Tax on reclassification from accumulated other comprehensive income	10	10	(31)
Discontinued Operations [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax on change in other comprehensive income (loss) before reclassifications	(3)	3	(16)
Tax on reclassification from accumulated other comprehensive income	16	10	21
Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax on change in other comprehensive income (loss) before reclassifications	1	4	(1)
Tax on reclassification from accumulated other comprehensive income	0	(2)	(1)
Pension Liability [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax on change in other comprehensive income (loss) before reclassifications	132	(165)	76
Tax on reclassification from accumulated other comprehensive income	(7)	(12)	(8)
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Tax on change in other comprehensive income (loss) before reclassifications	0	0	0
Tax on reclassification from accumulated other comprehensive income	$ 0	$ 0	$ 0