Revenue Recognized Under Previous Guidance New Accounting Pronouncements or Change in Accounting Principle (Balance Sheet) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017	Jan. 01, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net	$ 1,338	$ 1,270
Other current assets	283	243
Total current assets	2,791	2,830
Deferred income taxes	474	460
Other assets	607	586
Assets	7,641	7,654
Accounts payable	697	762
Contract liabilities	538	458
Other current liabilities	385	398
Liabilities, Current	1,844	1,889
Liabilities	6,201	6,107
Retained earnings	782	857
Stockholders' Equity Attributable to Parent	599	719
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	602	722	$ 736
Liabilities and Equity	7,641	$ 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	1,360
Other current assets	259
Total current assets	2,789
Deferred income taxes	476
Other assets	594
Assets	7,628
Contract liabilities	533
Other current liabilities	383
Liabilities, Current	1,837
Liabilities	6,194
Retained earnings	776
Stockholders' Equity Attributable to Parent	593
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	596
Liabilities and Equity	7,628
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	(5)
Other current liabilities	(2)
Liabilities, Current	(7)
Liabilities	(7)
Retained earnings	(6)
Stockholders' Equity Attributable to Parent	(6)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(6)
Liabilities and Equity	$ (13)