Employee Benefit Plans (Net Periodic Benefit Costs and Other Changes Recognized in OCI) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net Periodic Benefit Cost Amortized From Accumulated Other Comprehensive Income (Loss) [Abstract]
Total recognized in OCI	$ 1,001	$ (1,191)	$ 766
Pension Benefits U.S. Plans [Member]
Net periodic benefit costs [Abstract]
Service costs	200	214	195
Interest costs	437	366	383
Settlement and curtailment costs	14	0	0
Expected return on plan assets	(475)	(453)	(456)
Amortization of net actuarial (gains) losses	169	219	188
Amortization of prior service costs (credit)	1	6	6
Allocated to affiliates	292	340	304
Total net periodic benefit costs (credit)	292	340	304
Net Periodic Benefit Cost Amortized From Accumulated Other Comprehensive Income (Loss) [Abstract]
Net actuarial (gains) losses	996	(492)	705
Prior service costs (credit)	(18)	0	0
Amortization of net actuarial (gains) losses	(169)	(219)	(189)
Amortization of prior service (costs) credit	(1)	(6)	(6)
Total recognized in OCI	808	(717)	510
Total recognized in net periodic benefit costs and OCI	1,100	(377)	814
Pension Benefits U.S. Plans [Member] | Affiliated Entity [Member]
Net periodic benefit costs [Abstract]
Allocated to affiliates	(54)	(12)	(12)
Total net periodic benefit costs (credit)	(54)	(12)	(12)
Other Postretirement Benefits U.S. Plans [Member]
Net periodic benefit costs [Abstract]
Service costs	14	17	31
Interest costs	92	85	97
Settlement and curtailment costs	2	0	0
Expected return on plan assets	(75)	(74)	(76)
Amortization of net actuarial (gains) losses	11	51	53
Amortization of prior service costs (credit)	(1)	(69)	(97)
Allocated to affiliates	32	10	7
Total net periodic benefit costs (credit)	32	10	7
Net Periodic Benefit Cost Amortized From Accumulated Other Comprehensive Income (Loss) [Abstract]
Net actuarial (gains) losses	222	(532)	232
Prior service costs (credit)	(12)	0	0
Amortization of net actuarial (gains) losses	(11)	(55)	(57)
Amortization of prior service (costs) credit	1	75	104
Total recognized in OCI	200	(512)	279
Total recognized in net periodic benefit costs and OCI	232	(502)	286
Other Postretirement Benefits U.S. Plans [Member] | Affiliated Entity [Member]
Net periodic benefit costs [Abstract]
Allocated to affiliates	(11)	0	(1)
Total net periodic benefit costs (credit)	$ (11)	$ 0	$ (1)