Derivatives (Details 6) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Offsetting of Financial Liabilities under Master Netting Agreements with Derivative Counterparties
Gross Amounts of Derivative Liabilities Presented in the Consolidated Balance Sheet	$ 73	$ 43
Net Amount of Derivative Liabilities	35	23
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	68	36
Gross Amount of Eligible Offsetting Recognized Derivative Assets	38	20
Cash Collateral Pledged	0	0
Net Amount of Derivative Liabilities	30	16
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	5	7
Net Amount of Derivative Liabilities	$ 5	$ 7