Retirement and Employee Benefit Plans Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	$ 38	$ 9
Projected benefit obligation	198	205
Liability, Defined Benefit Plan, Noncurrent	22
Accumulated benefit obligation for defined benefit pension plans	35	3
Employer contributions	23	6
Estimated future employer contributions in next fiscal year, cash	5
Level 2 [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets	133	118
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Contribution expenses related to the defined contribution plans which cover certain employees	$ 24	$ 30	$ 66