Employee Benefit Plans - Schedule of Benefit Plan Components (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	221	232	663	696
Expected return on plan assets	(220)	(207)	(660)	(621)
Amortization of prior service credit	0	0	0	0
Recognized net actuarial loss	61	33	177	100
Net periodic cost	62	58	180	175
Other Postretirement and Postemployment Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	16	13	48	39
Interest cost	35	39	105	117
Expected return on plan assets	(20)	(21)	(60)	(63)
Amortization of prior service credit	(7)	(6)	(21)	(20)
Recognized net actuarial loss	6	1	18	3
Net periodic cost	$ 30	$ 26	$ 90	$ 76