Income Taxes (Net Operating Loss Carryforwards and Tax Credit Carryforwards) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Internal Revenue Service (IRS) [Member]
Net Operating Loss Carryforwards	$ 1,157	$ 1,698
Tax Credit Carryforward	33	29
State and Local Jurisdiction [Member]
Net Operating Loss Carryforwards	2,371	2,468
Net Operating Loss Carryforwards, Valuation allowance	59	54
Tax Credit Carryforward	$ 4	$ 4