Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), beginning			$ (936)
Shareholders' other comprehensive income (loss)	$ (191)	$ 160	(189)	$ 248
Accumulated other comprehensive income (loss), ending	(1,125)		(1,125)
Realized investment (gains) losses	(21)	(65)	(94)	(107)
Other operating expenses	2,212	1,996	4,416	3,976
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), before tax, beginning	1,083	864	955	733
Other comprehensive income (loss) before reclassifications, pre-tax	(337)	157	(189)	313
Reclassification adjustment, pre-tax	(13)	(4)	(33)	(29)
Other comprehensive income (loss), pre-tax	(350)	153	(222)	284
Accumulated other comprehensive income (loss), before tax, ending	733	1,017	733	1,017
Accumulated other comprehensive income/loss tax (expense) benefit, beginning	(375)	(301)	(335)	(256)
Other comprehensive income (loss), securities, before reclassifications, tax (expense) benefit	112	(51)	64	(105)
Reclassification adjustment, securities, tax (expense) benefit	4	1	12	10
Other comprehensive income (loss), tax (expense) benefit	116	(50)	76	(95)
Accumulated other comprehensive income/loss tax (expense) benefit, ending	(259)	(351)	(259)	(351)
Accumulated other comprehensive income (loss), beginning	708	563	620	477
Other comprehensive income (loss) before reclassifications, after-tax	(225)	106	(125)	208
Reclassification adjustment, after-tax	(9)	(3)	(21)	(19)
Shareholders' other comprehensive income (loss)	(234)	103	(146)	189
Accumulated other comprehensive income (loss), ending	474	666	474	666
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Realized investment (gains) losses	(13)	(4)	(33)	(29)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), before tax, beginning	(2)	(29)	(12)	(29)
Other comprehensive income (loss) before reclassifications, pre-tax	(3)		7
Reclassification adjustment, pre-tax	12		12
Other comprehensive income (loss), pre-tax	9	0	19	0
Accumulated other comprehensive income (loss), before tax, ending	7	(29)	7	(29)
Accumulated other comprehensive income/loss tax (expense) benefit, beginning	1	10	4	10
Other comprehensive income (loss), derivatives, before reclassifications, tax (expense) benefit	0		(3)
Reclassification adjustment, derivatives, tax (expense) benefit	(4)		(4)
Other comprehensive income (loss), tax (expense) benefit	(4)	0	(7)	0
Accumulated other comprehensive income/loss tax (expense) benefit, ending	(3)	10	(3)	10
Accumulated other comprehensive income (loss), beginning	(1)	(19)	(8)	(19)
Other comprehensive income (loss) before reclassifications, after-tax	(3)		4
Reclassification adjustment, after-tax	8		8
Shareholders' other comprehensive income (loss)	5	0	12	0
Accumulated other comprehensive income (loss), ending	4	(19)	4	(19)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Other operating expenses	12		12
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), before tax, beginning	(180)	78	(71)	91
Other comprehensive income (loss), pre-tax	15	51	(94)	38
Accumulated other comprehensive income (loss), before tax, ending	(165)	129	(165)	129
Accumulated other comprehensive income/loss tax (expense) benefit, beginning	14	(7)	9	(9)
Other comprehensive income (loss), tax (expense) benefit	3	(5)	8	(3)
Accumulated other comprehensive income/loss tax (expense) benefit, ending	17	(12)	17	(12)
Accumulated other comprehensive income (loss), beginning	(166)	71	(62)	82
Shareholders' other comprehensive income (loss)	18	46	(86)	35
Accumulated other comprehensive income (loss), ending	(148)	117	(148)	117
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), before tax, beginning	(2,270)	(1,611)	(2,286)	(1,630)
Other comprehensive income (loss) before reclassifications, pre-tax	12	2	12	2
Reclassification adjustment, pre-tax	18	15	34	34
Other comprehensive income (loss), pre-tax	30	17	46	36
Accumulated other comprehensive income (loss), before tax, ending	(2,240)	(1,594)	(2,240)	(1,594)
Accumulated other comprehensive income/loss tax (expense) benefit, beginning	795	563	800	570
Other comprehensive income (loss), postretirement benefits, before reclassifications, tax (expense) benefit	(3)	(1)	(3)	(1)
Reclassification adjustment, postretirement benefits, tax (expense) benefit	(7)	(5)	(12)	(12)
Other comprehensive income (loss), tax (expense) benefit	(10)	(6)	(15)	(13)
Accumulated other comprehensive income/loss tax (expense) benefit, ending	785	557	785	557
Accumulated other comprehensive income (loss), beginning	(1,475)	(1,048)	(1,486)	(1,060)
Other comprehensive income (loss) before reclassifications, after-tax	9	1	9	1
Reclassification adjustment, after-tax	11	10	22	22
Shareholders' other comprehensive income (loss)	20	11	31	23
Accumulated other comprehensive income (loss), ending	(1,455)	(1,037)	(1,455)	(1,037)
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Other operating expenses	18	15	34	34
Accumulated Defined Benefit Plans Adjustment Net Prior Service Cost Credit [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Reclassification adjustment, pre-tax	18	15	34	28
Reclassification adjustment, postretirement benefits, tax (expense) benefit	(7)	(5)	(12)	(10)
Reclassification adjustment, after-tax	11	10	22	18
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	$ 18	$ 15	$ 34	28
Accumulated Defined Benefit Plans Adjustment Settlement [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 Settlement [Member] | Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Other operating expenses				$ 6