Derivatives (Details 6) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Offsetting of Financial Liabilities under Master Netting Agreements with Derivative Counterparties
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	$ 43	$ 110
Net Amount of Derivative Liabilities	23	59
Derivatives Subject to Master Netting Agreements
Offsetting of Financial Liabilities under Master Netting Agreements with Derivative Counterparties
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	36	110
Gross Amount of Eligible Offsetting Recognized Derivative Assets	20	51
Cash Collateral Pledged	0	0
Net Amount of Derivative Liabilities	16	59
Derivatives Not Subject to Master Netting Agreements
Offsetting of Financial Liabilities under Master Netting Agreements with Derivative Counterparties
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	7	0
Net Amount of Derivative Liabilities	$ 7	$ 0