Employee Benefit Plans (Accumulated Other Comprehensive Loss Pretax Amounts Not Yet Reflected in Net Periodic Benefit Cost) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Total	$ 4,839	$ 4,701
Pensions
Defined Benefit Plan Disclosure [Line Items]
Accumulated net actuarial losses	1,910	1,542
Accumulated prior service credit	(20)	(26)
Total	1,890	1,516
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Accumulated net actuarial losses	366	254
Accumulated prior service credit	(34)	(45)
Total	$ 332	$ 209