Changes in Accumulated Other Comprehensive Income (Loss) by Component (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Changes in Accumulated other comprehensive income (loss) [Roll Forward]
Accumulated other comprehensive income (loss), beginning balance	$ 126		$ 831
Other comprehensive income (loss), before reclassifications	(16)		(722)
Amounts reclassified from accumulated other comprehensive income (loss)	(3)		(4)
Other comprehensive income (loss), net of tax	(13)	263	(718)	650
Accumulated other comprehensive income (loss), ending balance	113		113
Other comprehensive income (loss), tax, portion attributable to parent, parenthetical disclosures [Abtract]
Tax (expense) benefit on amounts reclassified from accumulated other comprehensive income (loss)	1		3
Tax (expense) benefit on other comprehensive income (loss)	36		377
Net unrealized gains (losses) on investments with OTTI Losses [Member]
Changes in Accumulated other comprehensive income (loss) [Roll Forward]
Accumulated other comprehensive income (loss), beginning balance	26		20
Other comprehensive income (loss), before reclassifications	(4)		2
Amounts reclassified from accumulated other comprehensive income (loss)	(1)		(1)
Other comprehensive income (loss), net of tax	(3)		3
Accumulated other comprehensive income (loss), ending balance	23		23
Other comprehensive income (loss), tax, portion attributable to parent, parenthetical disclosures [Abtract]
Tax (expense) benefit on amounts reclassified from accumulated other comprehensive income (loss)
Tax (expense) benefit on other comprehensive income (loss)	1		(2)
Net unrealized gains (losses) on other investments [Member]
Changes in Accumulated other comprehensive income (loss) [Roll Forward]
Accumulated other comprehensive income (loss), beginning balance	724		1,371
Other comprehensive income (loss), before reclassifications	(68)		(706)
Amounts reclassified from accumulated other comprehensive income (loss)	2		11
Other comprehensive income (loss), net of tax	(70)		(717)
Accumulated other comprehensive income (loss), ending balance	654		654
Other comprehensive income (loss), tax, portion attributable to parent, parenthetical disclosures [Abtract]
Tax (expense) benefit on amounts reclassified from accumulated other comprehensive income (loss)	(2)		(5)
Tax (expense) benefit on other comprehensive income (loss)	38		387
Pension and postretirement benefits [Member]
Changes in Accumulated other comprehensive income (loss) [Roll Forward]
Accumulated other comprehensive income (loss), beginning balance	(711)		(721)
Other comprehensive income (loss), before reclassifications
Amounts reclassified from accumulated other comprehensive income (loss)	(4)		(14)
Other comprehensive income (loss), net of tax	4		14
Accumulated other comprehensive income (loss), ending balance	(707)		(707)
Other comprehensive income (loss), tax, portion attributable to parent, parenthetical disclosures [Abtract]
Tax (expense) benefit on amounts reclassified from accumulated other comprehensive income (loss)	3		8
Tax (expense) benefit on other comprehensive income (loss)	(3)		(8)
Cumulative foreign currency translation adjustment [Member]
Changes in Accumulated other comprehensive income (loss) [Roll Forward]
Accumulated other comprehensive income (loss), beginning balance	87		161
Other comprehensive income (loss), before reclassifications	56		(18)
Amounts reclassified from accumulated other comprehensive income (loss)
Other comprehensive income (loss), net of tax	56		(18)
Accumulated other comprehensive income (loss), ending balance	143		143
Other comprehensive income (loss), tax, portion attributable to parent, parenthetical disclosures [Abtract]
Tax (expense) benefit on amounts reclassified from accumulated other comprehensive income (loss)
Tax (expense) benefit on other comprehensive income (loss)