Income Taxes Level 4 (Details) - Summary of the Valuation Allowance - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Valuation Allowance [Line Items]
Income Tax Expense (Benefit)	$ 38	$ 34	$ 22
Deferred Tax Assets, Operating Loss Carryforwards, Domestic	1,059
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	611	588	518
Changes in Related Gross Deferred Tax Assets/Liabilities	(2)	6	4
Charge	42	17	66
Balance at End of Period	651	$ 611	$ 588
Tax Credit Carryforward, Amount	2
Valuation allowance on state net operating loss carryforwards	69
Operating Loss Carryforwards, Valuation Allowance	$ 83