Income Taxes - Operating Loss Carryforwards and Tax Carryforwards (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ 931	$ 982
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	15,325
Valuation allowance on operating loss carryforwards	14,126
Tax Year 2033 [Member] | Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	403
Expiration Period, 2013-2018 [Member] | State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	502
Tax credit carryforwards	9
Expiration Period, 2018-2023 [Member] | State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	1,017
Expiration Period, 2023-2028 [Member] | State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	4,374
Expiration Period, 2029 and Thereafter [Member] | State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	9,432
No Expiration [Member] | State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	3
General Business Tax Credit Carryforward [Member] | State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	12
2018 [Member] | Foreign Tax Credits [Member] | Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	12
2029 [Member] | General Business Tax Credit Carryforward [Member] | Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 8