Income Taxes Income taxes (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Operating Loss Carryforwards [Line Items]
Tax Credit Carryforward, Federal	$ 42
Tax Credit Carryforward, State	4
Deferred Tax Assets, Valuation Allowance	0	$ 0
Unrecognized Tax Benefits	$ 0	$ 0