Income Taxes Level 4 AMT credit and foreign tax credit carryover (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Tax Credit Carryforwards, Foreign	$ 33	$ 56
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	742	640
Deferred Tax Assets, Tax Credit Carryforwards, General Business	$ 3	$ 99
Tax Credit Carryforward, Expiration Date	Dec. 31, 2022