Revenue Recognized Under Previous Guidance New Accounting Pronouncements or Change in Accounting Principle (Balance Sheet) (Details) - USD ($) $ in Millions	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net	$ 1,309		$ 1,270
Other current assets	296		243
Total current assets	2,855		2,830
Deferred income taxes	488		460
Other assets	591		586
Assets	7,505		7,654
Contract liabilities	427		458
Other current liabilities	302		398
Liabilities, Current	2,004		1,889
Liabilities	6,197		6,107
Retained earnings	666		857
Stockholders' Equity Attributable to Parent	444		719
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	448	$ 737	722
Liabilities and Equity	7,505		$ 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	1,322
Other current assets	289
Total current assets	2,861
Deferred income taxes	494
Other assets	564
Assets	7,490
Contract liabilities	428
Other current liabilities	300
Liabilities, Current	2,003
Liabilities	6,196
Retained earnings	652
Stockholders' Equity Attributable to Parent	430
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	434
Liabilities and Equity	7,490
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	13
Other current assets	(7)
Total current assets	6
Deferred income taxes	6
Other assets	(27)
Assets	(15)
Contract liabilities	1
Other current liabilities	(2)
Liabilities, Current	(1)
Liabilities	(1)
Retained earnings	(14)
Stockholders' Equity Attributable to Parent	(14)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(14)
Liabilities and Equity	$ (15)