Income Taxes Level 4 Net Operating Loss Carrryover (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	$ 0	$ 3,301
Expiring within Tax Years 2023 to 2033 [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	$ 0
Earliest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2023
Latest Tax Year [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date	Dec. 31, 2033