Changes in Accumulated Other Comprehensive Income (Loss) by Component (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Changes in Accumulated other comprehensive income (loss) [Roll Forward]
Accumulated other comprehensive income (loss), beginning balance	$ 831
Other comprehensive income (loss), before reclassifications	(96)
Amounts reclassified from accumulated other comprehensive income (loss)	8
Other comprehensive income (loss), net of tax	(104)	284
Accumulated other comprehensive income (loss), ending balance	727
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)
Tax (expense) benefit on other comprehensive income (loss), tax	25
Net unrealized gains (losses) on investments with OTTI losses, tax [Member]
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), tax	(7)
Net unrealized gains (losses) on other investments, tax [Member]
Other comprehensive income (loss), tax, portion attributable to parent, parenthetical disclosures [Abtract]
Tax (expense) benefit on amounts reclassified from accumulated other comprehensive income (loss)	(6)
Tax (expense) benefit on other comprehensive income (loss), tax	35
Pension and postretirement benefits member, tax [Member]
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
Tax (expense) benefit on other comprehensive income (loss), tax	(3)
Cumulative foreign currency translation adjustment, tax [Member]
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), tax
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	20
Other comprehensive income (loss), before reclassifications	14
Amounts reclassified from accumulated other comprehensive income (loss)
Other comprehensive income (loss), net of tax	14
Accumulated other comprehensive income (loss), ending balance	34
Net unrealized gains (losses) on other investments [Member]
Changes in Accumulated other comprehensive income (loss) [Roll Forward]
Accumulated other comprehensive income (loss), beginning balance	1,371
Other comprehensive income (loss), before reclassifications	(49)
Amounts reclassified from accumulated other comprehensive income (loss)	13
Other comprehensive income (loss), net of tax	(62)
Accumulated other comprehensive income (loss), ending balance	1,309
Pension and postretirement benefits [Member]
Changes in Accumulated other comprehensive income (loss) [Roll Forward]
Accumulated other comprehensive income (loss), beginning balance	(721)
Other comprehensive income (loss), before reclassifications
Amounts reclassified from accumulated other comprehensive income (loss)	(5)
Other comprehensive income (loss), net of tax	5
Accumulated other comprehensive income (loss), ending balance	(716)
Cumulative foreign currency translation adjustment [Member]
Changes in Accumulated other comprehensive income (loss) [Roll Forward]
Accumulated other comprehensive income (loss), beginning balance	161
Other comprehensive income (loss), before reclassifications	(61)
Amounts reclassified from accumulated other comprehensive income (loss)
Other comprehensive income (loss), net of tax	(61)
Accumulated other comprehensive income (loss), ending balance	$ 100