Income Taxes - Operating Loss Carryforwards and Tax Carryforwards (Details) $ in Millions	Dec. 31, 2016 USD ($)
Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 5,271
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	14,417
Valuation allowance on operating loss carryforwards	12,831
General Business Tax Credit Carryforward [Member] | State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	11
Valuation allowance on tax credit carryforward, Valuation Allowance	7
Tax Year 2033 [Member] | Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	1,554
Tax Year 2034 [Member] | Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	696
Tax Year 2035 [Member] | Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	491
Tax Year 2036 [Member] | Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	2,530
Tax Years 2016 - 2020 [Member] | State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	291
Tax Years 2016 - 2019 [Member] | General Business Tax Credit Carryforward [Member] | State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	1
Tax Years 2021 - 2025 [Member] | State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	1,757
Tax Years 2026 - 2030 [Member] | State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	8,134
Tax Year 2031 [Member] | State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	4,235
No Expiration [Member] | General Business Tax Credit Carryforward [Member] | State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforwards	$ 10