Income Taxes Level 4 Unrecognized tax benefit (expense) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits			$ 12	$ 48	$ 48
Unrecognized Tax Benefits, Increase Resulting from Prior Period Tax Positions	$ 12		12
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions		$ (48)	$ (48)