Income Taxes Level 4 AMT credit and foreign tax credit carryover (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Tax Credit Carryforwards, Foreign	$ 42	$ 56
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	777	640
Deferred Tax Assets, Tax Credit Carryforwards, General Business	$ 2	99
Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Tax Credit Carryforward, Expiration Date	Dec. 31, 2021
Expiring within Tax Years 2021 to 2024 [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Tax Credit Carryforwards, Foreign	$ 42
No expiration tax year [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	$ 777
Latest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Tax Credit Carryforward, Expiration Date	Dec. 31, 2035
Expiring Tax Year 2031 to 2035 [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Tax Credit Carryforwards, General Business	$ 2
Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Tax Credit Carryforward, Deferred Tax Asset	$ 42	$ 56