Benefit Plans (Funded Status) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at January 1	$ 3,019	$ 2,943
Service cost	4	9	$ 12
Interest cost	112	132	121
Participants' contributions	0	0
Plan amendments	(55)	(3)
Actuarial (gain) loss	(79)	367
Benefits paid	(173)	(165)
Settlements	0	(257)
Foreign currency translation and other	(7)	(7)
Benefit obligation at December 31	2,821	3,019	2,943
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at January 1	2,456	2,656
Actual return on plan assets	(18)	216
Company contributions	10	12
Participants' contributions	0	0
Benefits paid	(173)	(165)
Settlements	0	(257)
Foreign currency translation and other	(8)	(6)
Fair value of plan assets at December 31	2,267	2,456	2,656
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded status	(554)	(563)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Other assets	12	9
Other liabilities	(566)	(572)
Net amount recognized on balance sheets	(554)	(563)
Amounts recognized in Accumulated other comprehensive income not yet recognized in net periodic cost (benefit)[Abstract]
Prior service credit	0	0
Net actuarial (gain) loss	999	974
Net amount recognized in Accumulated other comprehensive income	999	974
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at January 1	29	40
Service cost	0	0	1
Interest cost	1	1	1
Participants' contributions	4	5
Plan amendments	0	(7)
Actuarial (gain) loss	(3)	1
Benefits paid	(8)	(11)
Settlements	0	0
Foreign currency translation and other	0	0
Benefit obligation at December 31	23	29	40
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at January 1	0	0
Actual return on plan assets	0	0
Company contributions	4	6
Participants' contributions	4	5
Benefits paid	(8)	(11)
Settlements	0	0
Foreign currency translation and other	0	0
Fair value of plan assets at December 31	0	0	$ 0
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded status	(23)	(29)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Other assets	0	0
Other liabilities	(23)	(29)
Net amount recognized on balance sheets	(23)	(29)
Amounts recognized in Accumulated other comprehensive income not yet recognized in net periodic cost (benefit)[Abstract]
Prior service credit	(6)	(9)
Net actuarial (gain) loss	3	8
Net amount recognized in Accumulated other comprehensive income	$ (3)	$ (1)