Revenue Recognized Under Previous Guidance New Accounting Pronouncements or Change in Accounting Principle (Balance Sheet) (Details) - USD ($) $ in Millions	Jun. 30, 2018	Dec. 31, 2017	Jan. 01, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net	$ 1,272	$ 1,270
Other current assets	282	243
Total current assets	2,739	2,830
Deferred income taxes	472	460
Other assets	593	586
Assets	7,364	7,654
Accounts payable	711	762
Contract liabilities	469	458
Other current liabilities	310	398
Liabilities, Current	1,879	1,889
Liabilities	6,144	6,107
Retained earnings	594	857
Stockholders' Equity Attributable to Parent	371	719
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	374	722	$ 737
Liabilities and Equity	7,364	$ 7,654
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net	1,294
Other current assets	258
Total current assets	2,737
Deferred income taxes	474
Other assets	580
Assets	7,351
Contract liabilities	466
Other current liabilities	308
Liabilities, Current	1,874
Liabilities	6,139
Retained earnings	586
Stockholders' Equity Attributable to Parent	363
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	366
Liabilities and Equity	7,351
Accounting Standards Update 2014-09 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net	22
Other current assets	(24)
Total current assets	(2)
Deferred income taxes	2
Other assets	(13)
Assets	(13)
Contract liabilities	(3)
Other current liabilities	(2)
Liabilities, Current	(5)
Liabilities	(5)
Retained earnings	(8)
Stockholders' Equity Attributable to Parent	(8)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(8)
Liabilities and Equity	$ (13)