Revenue Recognition - Reported Results Under ASC 606 (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	$ 5,902	$ 4,090	$ 11,847	$ 8,299
Cost of services and products (exclusive of depreciation and amortization)	2,730	1,890	5,533	3,778
Selling, general and administrative	1,115	884	2,224	1,694
Income tax (benefit) expense	(55)	23	66	167
Net income	$ 292	$ 17	$ 407	$ 180
BASIC AND DILUTED EARNINGS PER COMMON SHARE
BASIC (in dollars per share)	$ 0.27	$ 0.03	$ 0.38	$ 0.33
DILUTED (in dollars per share)	$ 0.27	$ 0.03	$ 0.38	$ 0.33
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING
BASIC (in shares)	1,064,711,000	541,361,000	1,064,663,000	540,909,000
DILUTED (in shares)	1,068,819,000	542,151,000	1,068,414,000	541,836,000
Other current assets	$ 1,260		$ 1,260		$ 941
Other long-term assets, net	1,123		1,123		1,286
Contract liabilities	2,379		2,379
Deferred income taxes, net	2,407		2,407		2,413
Other long-term liabilities	2,667		2,667		2,389
Retained earnings	1,040		1,040		$ 1,103
Impact of ASC 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	11		26
Cost of services and products (exclusive of depreciation and amortization)	3		10
Selling, general and administrative	10		26
Income tax (benefit) expense	0		(2)
Net income	$ (2)		$ (8)
BASIC AND DILUTED EARNINGS PER COMMON SHARE
BASIC (in dollars per share)	$ 0.00		$ 0.00
DILUTED (in dollars per share)	$ 0.00		$ 0.00
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING
BASIC (in shares)	0		0
DILUTED (in shares)	0		0
Other current assets	$ (125)		$ (125)
Other long-term assets, net	(103)		(103)
Contract liabilities	132		132
Deferred income taxes, net	(102)		(102)
Other long-term liabilities	49		49
Retained earnings	(307)		(307)
ASC 605 Historical Adjusted Balances
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	5,913		11,873
Cost of services and products (exclusive of depreciation and amortization)	2,733		5,543
Selling, general and administrative	1,125		2,250
Income tax (benefit) expense	(55)		64
Net income	$ 290		$ 399
BASIC AND DILUTED EARNINGS PER COMMON SHARE
BASIC (in dollars per share)	$ 0.27		$ 0.38
DILUTED (in dollars per share)	$ 0.27		$ 0.38
WEIGHTED-AVERAGE COMMON SHARES OUTSTANDING
BASIC (in shares)	1,064,711,000		1,064,663,000
DILUTED (in shares)	1,068,819,000		1,068,414,000
Other current assets	$ 1,135		$ 1,135
Other long-term assets, net	1,020		1,020
Contract liabilities	2,511		2,511
Deferred income taxes, net	2,305		2,305
Other long-term liabilities	2,716		2,716
Retained earnings	$ 733		$ 733