Retirement Benefits (Details 5) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Pension Benefits
Amounts expected to be recognized in 2014 net periodic benefit cost (Table Amounts)
Net actuarial loss	$ 682
Prior service credit	(60)
Medical and Life Benefits
Amounts expected to be recognized in 2014 net periodic benefit cost (Table Amounts)
Net actuarial loss	27
Prior service credit	$ (28)