v3.3.1.900
Retirement Benefits Plans - Other Postretirement Benefits Plan Assumptions (Details 8) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Defined Benefit Plan, Effect of One-Percentage Point Change in Assumed Health Care Cost Trend Rates [Abstract]      
Effect on total service and interest cost, 1% increase $ 1    
Effect on total service and interest cost, 1% decrease (1)    
Effect on other postretirement liabilities, 1% increase 17    
Effect on other postretirement liabilities, 1% decrease $ (16)    
Other postretirement benefits plans [Member]      
Assumptions used to determine benefit obligation at year-end      
Discount rate 4.04% 3.79% 4.48%
Health care cost trend rate assumed for next year 7.10% 6.31% 6.64%
Ultimate health care cost trend rate 4.75% 4.77% 4.77%
Year ultimate health care cost trend rate is achieved 2025 2024 2023
Assumptions used to determine expense      
Discount rate 3.79% 4.48% 3.79%
Initial health care cost trend rate 6.31% 6.64% 6.96%
Ultimate health care cost trend rate 4.77% 4.77% 4.53%
Year ultimate health care cost trend rate is achieved 2024 2023 2022