Products and Services Revenues - Effects of ASC 606 (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating revenues	$ 2,130	$ 2,162
Cost of services and products (exclusive of depreciation and amortization)	707	720
Selling, general and administrative	215	244
Income tax expense	130	$ 174
Net income	380
Other	217		$ 98
Other, net	100		75
Advance billings and customer deposits	255		265
Deferred income taxes, net	1,003		1,001
Other	80		82
Accumulated deficit	(505)		(713)
Impact of 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating revenues	(9)
Cost of services and products (exclusive of depreciation and amortization)	6
Selling, general and administrative	(1)
Income tax expense	(4)
Net income	(10)
Other	(109)
Other, net	(31)
Advance billings and customer deposits	1
Deferred income taxes, net	(41)
Other	27
Accumulated deficit	(138)		$ 128
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Operating revenues	2,121
Cost of services and products (exclusive of depreciation and amortization)	713
Selling, general and administrative	214
Income tax expense	126
Net income	370
Other	108
Other, net	69
Advance billings and customer deposits	256
Deferred income taxes, net	962
Other	107
Accumulated deficit	$ (643)