Income Taxes Income Taxes (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
Income Tax Contingency [Line Items]
Income tax expense	$ 82	$ 97	$ 185	$ 217
Income before income tax expense	$ 1,205	$ 190	$ 1,385	$ 1,020
Effective income tax rate	6.80%	51.10%	13.40%	21.30%
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	35.00%