Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Shareholders' other comprehensive income (loss)	$ 160	$ (258)	$ 248	$ (343)
Other realized investment (gains) losses	(66)	(34)	(108)	(173)
Other operating expenses	2,044	1,950	4,076	3,806
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, pre-tax	157	(384)	313	(420)
Reclassification adjustment, pre-tax	(4)	(23)	(29)	(93)
Other comprehensive income (loss), pre-tax	153	(407)	284	(513)
Other comprehensive income (loss), securities, before reclassifications, tax (expense) benefit	(51)	130	(105)	142
Reclassification adjustment, securities, tax (expense) benefit	1	8	10	32
Other comprehensive income (loss), tax (expense) benefit	(50)	138	(95)	174
Other comprehensive income (loss) before reclassifications, after-tax	106	(254)	208	(278)
Reclassification adjustment, after-tax	(3)	(15)	(19)	(61)
Shareholders' other comprehensive income (loss)	103	(269)	189	(339)
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other realized investment (gains) losses	(4)	(23)	(29)	(93)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), pre-tax	0	10	0	14
Other comprehensive income (loss), tax (expense) benefit	0	(4)	0	(5)
Shareholders' other comprehensive income (loss)	0	6	0	9
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), pre-tax	51	(23)	38	(92)
Other comprehensive income (loss), tax (expense) benefit	(5)	7	(3)	18
Shareholders' other comprehensive income (loss)	46	(16)	35	(74)
Accumulated Defined Benefit Plans Adjustment Net Prior Service Cost Credit [Member] | Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other operating expenses	15	17	28	34
Accumulated Defined Benefit Plans Adjustment Net Prior Service Cost Credit [Member] | Other Postretirement Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification adjustment, pre-tax	15	17	28	34
Reclassification adjustment, postretirement benefits, tax (expense) benefit	(5)	(6)	(10)	(12)
Reclassification adjustment, after-tax	10	11	18	22
Accumulated Defined Benefit Plans Adjustment Curtailment [Member] | Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other operating expenses				(19)
Accumulated Defined Benefit Plans Adjustment Curtailment [Member] | Other Postretirement Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification adjustment, pre-tax				(19)
Reclassification adjustment, postretirement benefits, tax (expense) benefit				7
Reclassification adjustment, after-tax				(12)
Accumulated Defined Benefit Plans Adjustment Settlement [Member] | Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other operating expenses			6
Accumulated Defined Benefit Plans Adjustment Settlement [Member] | Other Postretirement Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification adjustment, pre-tax			6
Reclassification adjustment, postretirement benefits, tax (expense) benefit			(2)
Reclassification adjustment, after-tax			4
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other operating expenses			34	15
Accumulated Defined Benefit Plans Adjustment [Member] | Other Postretirement Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, pre-tax	2	16	2	79
Reclassification adjustment, pre-tax			34	15
Other comprehensive income (loss), pre-tax	17	33	36	94
Reclassification adjustment, postretirement benefits, tax (expense) benefit			(12)	(5)
Other comprehensive income (loss), postretirement benefits, before reclassifications, tax (expense) benefit	(1)	(6)	(1)	(28)
Other comprehensive income (loss), tax (expense) benefit	(6)	(12)	(13)	(33)
Other comprehensive income (loss) before reclassifications, after-tax	1	10	1	51
Reclassification adjustment, after-tax			22	10
Shareholders' other comprehensive income (loss)	$ 11	$ 21	$ 23	$ 61