Fair Value of Financial Instruments Unobservable Input Reconciliation (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance as of the beginning of the period	$ 131	$ 45	$ 139	$ 16
Net realized and unrealized (gains) losses (1)	(44)	11	(55)	15
Purchases	0	0	0	25
Transfers out of Level 3 to Level 2	(2)	0	(5)	0
Balance as of the end of the period	$ 89	$ 56	$ 89	$ 56