Annual report pursuant to Section 13 and 15(d)

Pension and Other Postretirement Benefit Programs - Weighted Average Assumptions (Details)

v3.8.0.1
Pension and Other Postretirement Benefit Programs - Weighted Average Assumptions (Details)
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Retiree Health and Life Insurance Plans    
Weighted average assumptions used to determine benefit obligations as of December 31,    
Discount rate (in percentage) 3.60% 4.05%
Weighted average assumptions used to determine net periodic benefit cost for the period:    
Discount rate (in percentage) 4.05% 4.25%
U.S. Pension Plan | Pension Plan    
Weighted average assumptions used to determine benefit obligations as of December 31,    
Discount rate (in percentage) 3.75% 4.30%
Rate of compensation increase (in percentage) 3.25% 3.10%
Weighted average assumptions used to determine net periodic benefit cost for the period:    
Discount rate (in percentage) 4.30% 4.40%
Expected return on plan assets (in percentage) 6.10% 6.75%
Rate of compensation increase (in percentage) 3.10% 3.10%
Canadian Pension Plan | Pension Plan    
Weighted average assumptions used to determine benefit obligations as of December 31,    
Discount rate (in percentage) 3.30% 3.80%
Weighted average assumptions used to determine net periodic benefit cost for the period:    
Discount rate (in percentage) 3.80% 3.50%
Expected return on plan assets (in percentage) 5.40% 5.40%