Employee Benefit Plans (Obligations and Funded Status) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits
Change in benefit obligations:
Benefit obligations at January 1,	$ 10,506	$ 11,001
Service costs	272	276	$ 262
Interest costs	432	423	456
Plan participants’ contributions	0	0
Net actuarial (gains) losses	367	(627)
Acquisition, divestitures, settlements and curtailments	(36)	(4)
Change in benefits	(11)	0
Benefits paid	(591)	(531)
Effect of foreign currency translation	21	(32)
Benefit obligations at December 31,	10,960	10,506	11,001
Change in plan assets
Estimated fair value of plan assets at January 1,	8,751	9,003
Actual return on plan assets	630	(127)
Acquisition, divestitures and settlements	(7)	(3)
Plan participants’ contributions	0	0
Employer contributions	378	424
Benefits paid	(591)	(531)
Effect of foreign currency translation	3	(15)
Estimated fair value of plan assets at December 31,	9,164	8,751	9,003
Over (under) funded status at December 31,	(1,796)	(1,755)
Amounts recognized in the consolidated balance sheets
Other assets	5	5
Other liabilities	(1,801)	(1,760)
Net amount recognized	(1,796)	(1,755)
Accumulated other comprehensive (income) loss:
Net actuarial (gains) losses	2,993	2,945
Prior service costs (credit)	(11)	0
Accumulated other comprehensive (income) loss, before income tax	2,982	2,945
Accumulated benefit obligation	10,559	10,082
Other Postretirement Benefits
Change in benefit obligations:
Benefit obligations at January 1,	1,924	2,145
Service costs	9	17	16
Interest costs	84	90	94
Plan participants’ contributions	33	30
Net actuarial (gains) losses	(117)	(235)
Acquisition, divestitures, settlements and curtailments	27	(2)
Change in benefits	(44)	(7)
Benefits paid	(117)	(109)
Effect of foreign currency translation	(3)	(5)
Benefit obligations at December 31,	1,796	1,924	2,145
Change in plan assets
Estimated fair value of plan assets at January 1,	1,382	1,436
Actual return on plan assets	75	4
Acquisition, divestitures and settlements	(2)	(4)
Plan participants’ contributions	33	30
Employer contributions	17	26
Benefits paid	(117)	(109)
Effect of foreign currency translation	(2)	(1)
Estimated fair value of plan assets at December 31,	1,386	1,382	$ 1,436
Over (under) funded status at December 31,	(410)	(542)
Amounts recognized in the consolidated balance sheets
Other assets	1	1
Other liabilities	(411)	(543)
Net amount recognized	(410)	(542)
Accumulated other comprehensive (income) loss:
Net actuarial (gains) losses	89	222
Prior service costs (credit)	(49)	(14)
Accumulated other comprehensive (income) loss, before income tax	$ 40	$ 208