Pension and Other Postretirement Benefits, Weighted Average Assumptions Used to Determine Net Periodic Benefit Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Effect of one percentage point increase on total service and interest cost	$ 0
Effect of one percentage point decrease on total service and interest cost	0
Effect of one percentage point increase on postretirement benefit obligations	4
Effect of one percentage point decrease on postretirement benefit obligations	$ (4)
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation	3.78%	4.40%	4.67%
Service cost	3.84%	4.55%	4.83%
Interest cost	3.45%	3.84%	3.95%
Expected long-term return on plan assets	7.92%	7.92%	7.92%
Rate of compensation increase	3.50%	3.50%	3.50%
Pension Plans [Member] | U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation	3.81%	4.45%	4.73%
Expected long-term return on plan assets	8.00%	8.00%	8.00%
Rate of compensation increase	3.50%	3.50%	3.50%
Health care cost trend rate, covering retirees under 65 years of age next fiscal year	6.75%
Health care cost trend rate, covering retirees over 65 years of age next fiscal year	7.75%
Pension Plans [Member] | U.S. [Member] | 2028 and Thereafter [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate, covering retirees under 65 years of age	4.50%
Pension Plans [Member] | U.S. [Member] | 2032 and Thereafter [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate, covering retirees over 65 years of age	4.50%
Pension Plans [Member] | Canada [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation	3.39%	3.79%	3.93%
Expected long-term return on plan assets	7.25%	7.25%	7.25%
Rate of compensation increase	3.50%	3.50%	3.50%
Health care cost trend rate next fiscal year	7.00%
Pension Plans [Member] | Canada [Member] | 2028 and Thereafter [Member]
Defined Benefit Plan Disclosure [Line Items]
Health care cost trend rate	5.00%
Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation	3.59%	4.05%	4.22%
Service cost	3.64%	4.21%	4.37%
Interest cost	3.07%	3.26%	3.26%
Expected long-term return on plan assets	8.00%	7.43%	7.42%
Postretirement Benefit Plans [Member] | U.S. [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation	3.63%	4.11%	4.28%
Postretirement Benefit Plans [Member] | Canada [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation	3.33%	3.64%	3.74%