Employee Benefit Plans (Projected Benefit Obligation in Excess of Plan Assets) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Pension Benefits U.S. Plans [Member]
Defined Benefit Plan Pension Plans With Projected Benefit Obligations In Excess Of Plan Assets [Abstract]
Projected benefit obligations	$ 10,241	$ 1,170
Fair value of plan assets	8,719	133
Other Postretirement Benefits U.S. Plans [Member]
Defined Benefit Plan Pension Plans With Projected Benefit Obligations In Excess Of Plan Assets [Abstract]
Projected benefit obligations	2,129	1,863
Fair value of plan assets	$ 1,426	$ 1,353