Employee Benefit Plans (Accumulated Other Comprehensive Loss Pretax Amounts Not Yet Reflected in Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Total	$ 4,627	$ 4,839
Pensions
Defined Benefit Plan Disclosure [Line Items]
Accumulated net actuarial losses	1,872	1,910
Accumulated prior service credit	(18)	(20)
Total	1,854	1,890
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Accumulated net actuarial losses	228	366
Accumulated prior service credit	(24)	(34)
Total	$ 204	$ 332