Income Taxes Level 4 Net Operating Loss Carryover (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Tax Credit Carryforward, Valuation Allowance		$ 1
Deferred Tax Assets, Operating Loss Carryforwards, Domestic		1,814
Deferred Tax Assets, Operating Loss Carryforwards, Foreign		17
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	$ 684	639
Operating Loss Carryforwards, Valuation Allowance	$ 1
Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2016
Expiring within Tax Years 2016 to 2020 [Domain]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	$ 3
Latest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2033
Expiring within Tax Years 2023 to 2033 [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	$ 4,817
No expiration tax year [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	76
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	684
Domestic Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	4,820
Deferred Tax Assets, Operating Loss Carryforwards	1,687
Operating Loss Carryforwards		5,182
Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	76
Deferred Tax Assets, Operating Loss Carryforwards	$ 15
Operating Loss Carryforwards		$ 89

Amount before allocation of valuation allowances of deferred tax asset attributable to deductible operating loss carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible domestic operating loss carryforwards. Excludes state and local operating loss carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible foreign operating loss carryforwards.

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Amount before allocation of valuation allowances of deferred tax asset attributable to deductible alternative minimum tax credit carryforwards.

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Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

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Expiration date of each operating loss carryforward included in operating loss carryforward, in CCYY-MM-DD format.

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The portion of the valuation allowance pertaining to the deferred tax asset representing potential future taxable deductions from net operating loss carryforwards for which it is more likely than not that a tax benefit will not be realized.

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Amount of valuation allowance pertaining to the deferred tax asset representing potential future taxable deductions from tax credit carryforwards for which it is more likely than not that a tax benefit will not be realized.

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