Derivatives (Details 5) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Offsetting of Financial Assets under Master Netting Agreements with Derivative Counterparties
Gross Amounts of Derivative Assets Presented in the Consolidated Balance Sheet	$ 561	$ 256
Net Amounts of Derivative Assets	523	236
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	561	256
Gross Amount of Eligible Offsetting Recognized Derivative Liabilities	38	20
Cash Collateral Received	0	0
Net Amounts of Derivative Assets	523	236
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	0
Net Amounts of Derivative Assets	$ 0	$ 0