Retirement Benefits (Components of the Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost			$ 196	$ 213	$ 252
Interest cost			587	641	581
Expected return on plan assets			(977)	(990)	(911)
Amortization of prior service (credit) cost			(1)	(16)	(22)
Recognized actuarial loss (gain)			271	243	315
Net periodic benefit (credit) cost			76	91	215
Curtailment loss (gain)			5	(65)	0
Plan termination			0	0	0
Settlement loss			1	0	0
Total (credit) cost			82	26	215
U.S. Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost			114	91	104
Interest cost			254	253	229
Expected return on plan assets			(373)	(346)	(324)
Amortization of prior service (credit) cost				(7)	(16)
Recognized actuarial loss (gain)			146	112	207
Net periodic benefit (credit) cost			141	103	200
Total (credit) cost			141	103	200
Non-U.S. Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost			82	122	148
Interest cost			333	388	352
Expected return on plan assets			(604)	(644)	(587)
Amortization of prior service (credit) cost			(1)	(9)	(6)
Recognized actuarial loss (gain)			125	131	108
Net periodic benefit (credit) cost			(65)	(12)	15
Curtailment loss (gain)		$ (65)	5	(65)	0
Settlement loss			1	0	0
Total (credit) cost			(59)	(77)	15
Postretirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost			3	4	5
Interest cost			5	11	11
Expected return on plan assets			0	0	0
Amortization of prior service (credit) cost			3	0
Recognized actuarial loss (gain)			(1)	(1)	2
Net periodic benefit (credit) cost			10	14	18
Curtailment loss (gain)			0	0	0
Plan termination			(128)	0
Settlement loss			0	0	0
Total (credit) cost	$ (125)		(118)	14	18
U.S. Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost			1	2	3
Interest cost			2	7	7
Expected return on plan assets			0	0	0
Amortization of prior service (credit) cost			3	0
Recognized actuarial loss (gain)			(2)	(2)
Net periodic benefit (credit) cost			4	7	10
Plan termination			(128)
Total (credit) cost			(124)	7	10
Non-U.S. Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost			2	2	2
Interest cost			3	4	4
Expected return on plan assets			0	0	0
Amortization of prior service (credit) cost			0	0
Recognized actuarial loss (gain)			1	1	2
Net periodic benefit (credit) cost			6	7	8
Curtailment loss (gain)			0	0	0
Settlement loss			0	0	0
Total (credit) cost			$ 6	$ 7	$ 8