Fair Value Measurements (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Reconciliation of items measured at fair value on a recurring basis that used significant unobservable inputs (Level 3)
Balance at the beginning of the period	$ 10	$ 4	$ 7	$ 4
Total gains or losses included in earnings	0	0	0	0
Total gains or losses included in other comprehensive income	0	2	3	2
Purchases, issuances, and settlements	0	0	0	0
Transfers in and/or out of Level 3	0	0	0	0
Balance at the end of the period	10	6	10	6
Change in unrealized gains or losses for the period included in earnings for securities held at the end of the reporting period	$ 0	$ 0	$ 0	$ 0