Recent Accounting Pronouncements (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Recent Accounting Pronouncements
Retained earnings	$ 7,107	$ 6,381
Accumulated other comprehensive income, net of tax	605	1,194
Total equity	9,169	9,712	9,821	9,694
Accounting for Costs Associated with Acquiring or Renewing Insurance Contracts | Restatement for new accounting standard
Recent Accounting Pronouncements
Retained earnings				(1,400)
Accumulated other comprehensive income, net of tax				113
Total equity				$ (1,300)