Pension, Postretirement Health Care and Life Insurance Benefit Plans (Pension Plans with an accumulated benefit obligation in excess of plan assets) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Accumulated benefit obligation in excess of plan assets [Abstract]
Accumulated benefit obligation	$ 1,182	$ 1,059
Projected benefit obligation	1,182	1,059
Fair value of plan assets	$ 962	$ 920