Employee Benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	$ 30	$ 24	$ 28
Payment for Pension Benefits	9	2	$ 0
OtherPostretirementDefinedBenefitPlanLiabilityCurrent	2	$ 2
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year	11
Net actuarial loss portion of amortization from AOCL for pension benefits	10
Net Actuarial Loss Portion of Amortization from AOCL for Non-qualified benefits	$ 1
Defined benefit plan, current annual rate of health care cost increase	6.50%	6.50%	7.00%
Defined Benefit Plan, Assumed Health Care Cost Trend Rate, Description		0.06	0.065
Defined Benefit Plan, Health Care Cost Trend Rate Assumed, Next Fiscal Year	0.25%	0.25%	0.25%
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate	5.00%	5.00%	5.00%
Defined Benefit Plan, Effect of One Percentage Point Increase on Service and Interest Cost Components	$ 0
Company match pre 2009 hire	6.00%
Company match post 2008 hire	5.00%
Company contribution percentage to 401k for post 2008 hires	5.00%
Company contribution percent to 401k for bargaining employees	1.00%
401k Plan Company contributions	$ 23	$ 21	$ 19
Restatement Adjustment [Member]
Defined Benefit Plan Disclosure [Line Items]
Pension and Other Postretirement Benefits Cost (Reversal of Cost)	$ 5	$ 4	$ 7