Employee Benefit Plans - Schedule of Benefit Plan Components (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Pension Benefits
Defined Benefit Plan Disclosure
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	229	221	458	442
Expected return on plan assets	(226)	(220)	(452)	(440)
Amortization of prior service credit	0	0	0	0
Recognized net actuarial loss	59	58	118	116
Net periodic cost	62	59	124	118
Other Postretirement and Postemployment Benefits
Defined Benefit Plan Disclosure
Service cost	17	16	34	32
Interest cost	37	35	74	70
Expected return on plan assets	(18)	(20)	(36)	(40)
Amortization of prior service credit	(7)	(7)	(14)	(14)
Recognized net actuarial loss	6	6	12	12
Net periodic cost	$ 35	$ 30	$ 70	$ 60