Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Shareholders' other comprehensive income (loss)	$ 88	$ (85)
Other realized investment (gains) losses	(42)	(139)
Other operating expenses	2,032	1,856
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) before reclassifications, pre-tax	156	(36)
Reclassification adjustment, pre-tax	(25)	(70)
Other comprehensive income (loss), pre-tax	131	(106)
Other comprehensive income (loss), securities, before reclassifications, tax (expense) benefit	(54)	12
Reclassification adjustment, securities, tax (expense) benefit	9	24
Other comprehensive income (loss), tax (expense) benefit	(45)	36
Other comprehensive income (loss) before reclassifications, after-tax	102	(24)
Reclassification adjustment, after-tax	(16)	(46)
Shareholders' other comprehensive income (loss)	86	(70)
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	(25)	(70)
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	4
Other comprehensive income (loss), tax (expense) benefit	0	(1)
Shareholders' other comprehensive income (loss)	0	3
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), pre-tax	(13)	(69)
Other comprehensive income (loss), tax (expense) benefit	2	11
Shareholders' other comprehensive income (loss)	(11)	(58)
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	13	17
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	13	17
Reclassification adjustment, postretirement benefits, tax (expense) benefit	(5)	(6)
Reclassification adjustment, after-tax	8	11
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	19	(2)
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		63
Reclassification adjustment, pre-tax	19	(2)
Other comprehensive income (loss), pre-tax	19	61
Reclassification adjustment, postretirement benefits, tax (expense) benefit	(7)	1
Other comprehensive income (loss), postretirement benefits, before reclassifications, tax (expense) benefit		(22)
Other comprehensive income (loss), tax (expense) benefit	(7)	(21)
Other comprehensive income (loss) before reclassifications, after-tax		41
Reclassification adjustment, after-tax	12	(1)
Shareholders' other comprehensive income (loss)	$ 12	$ 40