Income Taxes Income Taxes - Net Operating Loss Carrryover (Details) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	$ 3,232,000,000	$ 3,243,000,000
Expiring within Tax Years 2023 to 2033 [Member]
Operating Loss Carryforwards [Line Items]
Expected Tax Benefit Attributable to Net Operating Losses Domestic Near term	3,229,000,000
Foreign Tax Credit Carryover [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards	$ 440,000,000