Derivatives (Details 5) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Offsetting of Financial Assets under Master Netting Agreements with Derivative Counterparties
Gross Amounts of Derivative Assets Presented in the Consolidated Balance Sheet	$ 256	$ 84
Net Amounts of Derivative Assets	236	33
Derivatives Subject to Master Netting Agreements
Offsetting of Financial Assets under Master Netting Agreements with Derivative Counterparties
Gross Amounts of Derivative Assets Presented in the Consolidated Balance Sheet	256	83
Gross Amount of Eligible Offsetting Recognized Derivative Liabilities	20	51
Cash Collateral Received	0	0
Net Amounts of Derivative Assets	236	32
Derivatives Not Subject to Master Netting Agreements
Offsetting of Financial Assets under Master Netting Agreements with Derivative Counterparties
Gross Amounts of Derivative Assets Presented in the Consolidated Balance Sheet	0	1
Net Amounts of Derivative Assets	$ 0	$ 1