Benefit Plans (Movements in Other Comprehensive Earnings (Losses)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Amortization:
Net losses	$ 257	$ 267	$ 189
Prior service cost	6	4	5
Other income/expense:
Net losses	4	3	16
Prior service cost	0	1	5
Deferred income taxes	(43)	(48)	(42)
Amortization of net losses, prior service costs and net transition costs, net of income taxes of ($43) in 2016, ($48) in 2015 and ($42) in 2014	224	227	173
Other movements during the year:
Deferred income taxes	78	17	167
Net gains (losses) and prior service costs	(460)	(536)	(1,148)
AOCI Attributable to Noncontrolling Interest [Member]
Other movements during the year:
Net losses	(517)	(556)	(1,309)
Prior service cost	(18)		(5)
Deferred income taxes	78	17	167
Net gains (losses) and prior service costs	(457)	(539)	(1,147)
Total movements in other comprehensive earnings (losses)	(233)	(312)	(974)
Pension [Member]
Amortization:
Net losses	193	194	121
Prior service cost	6	4	6
Other income/expense:
Net losses	4	3	14
Prior service cost	0	1	5
Deferred income taxes	(26)	(26)	(21)
Amortization of net losses, prior service costs and net transition costs, net of income taxes of ($43) in 2016, ($48) in 2015 and ($42) in 2014	177	176	125
Pension [Member] | AOCI Attributable to Noncontrolling Interest [Member]
Other movements during the year:
Net losses	(437)	(510)	(1,149)
Prior service cost	(18)		(5)
Deferred income taxes	55	4	118
Net gains (losses) and prior service costs	(400)	(506)	(1,036)
Total movements in other comprehensive earnings (losses)	(223)	(330)	(911)
Postretirement [Member]
Amortization:
Net losses	2	4	2
Prior service cost	0	0	(1)
Other income/expense:
Net losses	0	0	2
Prior service cost	0	0	0
Deferred income taxes	0	(2)	(1)
Amortization of net losses, prior service costs and net transition costs, net of income taxes of ($43) in 2016, ($48) in 2015 and ($42) in 2014	2	2	2
Other movements during the year:
Net losses	(15)	12	(34)
Prior service cost	0		0
Deferred income taxes	4	(4)	12
Net gains (losses) and prior service costs	(11)	8	(22)
Total movements in other comprehensive earnings (losses)	(9)	10	(20)
Postemployment Benefit Plans [Member]
Amortization:
Net losses	62	69	66
Prior service cost	0	0	0
Other income/expense:
Net losses	0	0	0
Prior service cost	0	0	0
Deferred income taxes	(17)	(20)	(20)
Amortization of net losses, prior service costs and net transition costs, net of income taxes of ($43) in 2016, ($48) in 2015 and ($42) in 2014	45	49	46
Other movements during the year:
Net losses	(65)	(58)	(126)
Prior service cost	0		0
Deferred income taxes	19	17	37
Net gains (losses) and prior service costs	(46)	(41)	(89)
Total movements in other comprehensive earnings (losses)	$ (1)	$ 8	$ (43)