Summary of Significant Accounting Principles and Practices - Schedule of Topic 606 Impact on the Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets
Receivables, net	$ 2,760	$ 2,730	$ 2,478
Other current assets	618	587	289
Deferred tax assets	561	261	389
Other non-current assets	448	452	307
Liabilities
Accounts payable and accrued liabilities	10,166	1,969	9,625
Other current liabilities	936	883	870
Deferred tax liabilities	181	169	127
Other non-current liabilities	1,097	1,099	1,102
Equity
Total equity	4,219	5,155	4,648	$ 5,532	$ 6,059
Calculated under Revenue Guidance in Effect before Topic 606
Assets
Receivables, net			2,478
Other current assets			289
Deferred tax assets			389
Other non-current assets			307
Liabilities
Accounts payable and accrued liabilities			1,961
Other current liabilities			870
Deferred tax liabilities			127
Other non-current liabilities			1,102
Equity
Total equity			$ 4,648
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Assets
Receivables, net	(301)	252
Other current assets	(319)	298
Deferred tax assets	137	(128)
Other non-current assets	(155)	145
Liabilities
Accounts payable and accrued liabilities		8
Other current liabilities	(43)	13
Deferred tax liabilities	(28)	42
Other non-current liabilities	2	(3)
Equity
Total equity	(569)	$ 507
Accounting Standards Update 2014-09 | Calculated under Revenue Guidance in Effect before Topic 606
Assets
Receivables, net	2,459
Other current assets	299
Deferred tax assets	698
Other non-current assets	293
Liabilities
Other current liabilities	893
Deferred tax liabilities	153
Other non-current liabilities	1,099
Equity
Total equity	$ 3,650