Basis of Presentation - Balance Sheet (Selected captions) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
ASSETS
Accounts receivable, net	$ 1,159	$ 1,198	$ 1,523
Contract assets	760	931	0
Inventories, net	391	328	327
Other current assets	330	284	832
Deferred income taxes	945	982	1,023
Other assets	420	418	333
LIABILITIES AND STOCKHOLDERS’ EQUITY
Contract liabilities	1,049	1,082	0
Accrued liabilities	1,096	1,187	2,286
Other liabilities	2,153	2,578	2,585
Retained earnings	627	594	467
Calculated under Revenue Guidance in Effect before Topic 606
ASSETS
Accounts receivable, net	1,364		1,523
Contract assets	0		0
Inventories, net			327
Other current assets	821		832
Deferred income taxes	986		1,023
Other assets	328		333
LIABILITIES AND STOCKHOLDERS’ EQUITY
Contract liabilities	0		0
Accrued liabilities	2,157		2,286
Other liabilities	2,163		2,585
Retained earnings	490		$ 467
Accounting Standards Update 2014-09 | Restatement Adjustment
ASSETS
Accounts receivable, net		(24)
Contract assets		0
Inventories, net		0
Other current assets		24
Deferred income taxes		0
Other assets		0
LIABILITIES AND STOCKHOLDERS’ EQUITY
Contract liabilities		1,099
Accrued liabilities		(1,099)
Other liabilities		0
Retained earnings		0
Accounting Standards Update 2014-09 | Restatement Adjustment | Contract Assets
ASSETS
Accounts receivable, net		(297)
Contract assets		846
Inventories, net		0
Other current assets		(549)
Deferred income taxes		0
Other assets		0
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
ASSETS
Accounts receivable, net	205	(4)
Contract assets	(760)	85
Inventories, net		1
Other current assets	491	(23)
Deferred income taxes	41	(41)
Other assets	(92)	85
LIABILITIES AND STOCKHOLDERS’ EQUITY
Contract liabilities	(1,049)	(17)
Accrued liabilities	1,061	0
Other liabilities	10	(7)
Retained earnings	$ (137)	$ 127