Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), January 1,	$ (936)
Shareholders' other comprehensive income (loss)	2	88
Accumulated other comprehensive income (loss), March 31,	(934)
Realized investment (gains) losses	(73)	(42)
Other operating expenses	2,204	1,980
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), before tax, January 1,	955	733
Other comprehensive income (loss) before reclassifications, pre-tax	148	156
Reclassification adjustment, pre-tax	(20)	(25)
Other comprehensive income (loss), pre-tax	128	131
Accumulated other comprehensive income (loss), before tax, March 31,	1,083	864
Accumulated Other Comprehensive Income/Loss Tax (Expense) Benefit, January 1,	(335)	(256)
Other comprehensive income (loss), securities, before reclassifications, tax (expense) benefit	(47)	(54)
Reclassification adjustment, securities, tax (expense) benefit	7	9
Other comprehensive income (loss), tax (expense) benefit	(40)	(45)
Other comprehensive income (loss) before reclassifications, after-tax	101	102
Accumulated Other Comprehensive Income/Loss Tax (Expense) Benefit, March 31,	(375)	(301)
Accumulated other comprehensive income (loss), January 1,	620	477
Reclassification adjustment, after-tax	(13)	(16)
Shareholders' other comprehensive income (loss)	88	86
Accumulated other comprehensive income (loss), March 31,	708	563
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	(20)	(25)
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, January 1,	(12)	(29)
Other comprehensive income (loss), pre-tax	10	0
Accumulated other comprehensive income (loss), before tax, March 31,	(2)	(29)
Accumulated Other Comprehensive Income/Loss Tax (Expense) Benefit, January 1,	4	10
Other comprehensive income (loss), tax (expense) benefit	(3)	0
Accumulated Other Comprehensive Income/Loss Tax (Expense) Benefit, March 31,	1	10
Accumulated other comprehensive income (loss), January 1,	(8)	(19)
Shareholders' other comprehensive income (loss)	7	0
Accumulated other comprehensive income (loss), March 31,	(1)	(19)
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), before tax, January 1,	(71)	91
Other comprehensive income (loss), pre-tax	(109)	(13)
Accumulated other comprehensive income (loss), before tax, March 31,	(180)	78
Accumulated Other Comprehensive Income/Loss Tax (Expense) Benefit, January 1,	9	(9)
Other comprehensive income (loss), tax (expense) benefit	5	2
Accumulated Other Comprehensive Income/Loss Tax (Expense) Benefit, March 31,	14	(7)
Accumulated other comprehensive income (loss), January 1,	(62)	82
Shareholders' other comprehensive income (loss)	(104)	(11)
Accumulated other comprehensive income (loss), March 31,	(166)	71
Accumulated Defined Benefit Plans Adjustment Net Prior Service Cost Credit [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Reclassification adjustment, pre-tax	16	13
Reclassification adjustment, postretirement benefits, tax (expense) benefit	(5)	(5)
Reclassification adjustment, after-tax	11	8
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	16	13
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
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Accumulated other comprehensive income (loss), before tax, January 1,	(2,286)	(1,630)
Reclassification adjustment, pre-tax	16	19
Accumulated other comprehensive income (loss), before tax, March 31,	(2,270)	(1,611)
Accumulated Other Comprehensive Income/Loss Tax (Expense) Benefit, January 1,	800	570
Reclassification adjustment, postretirement benefits, tax (expense) benefit	(5)	(7)
Accumulated Other Comprehensive Income/Loss Tax (Expense) Benefit, March 31,	795	563
Accumulated other comprehensive income (loss), January 1,	(1,486)	(1,060)
Reclassification adjustment, after-tax	11	12
Accumulated other comprehensive income (loss), March 31,	(1,475)	(1,048)
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification Out Of Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income Loss [Line Items]
Other operating expenses	$ 16	$ 19