New Accounting Standards Cumulative Effect of Changes due to Adoption (Details) - USD ($) $ in Millions	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other assets	$ 3,672	$ 3,922	$ 3,930
Other assets	9,459	9,253	7,929
Deferred Tax Liabilities, Net		10,408
Other Liabilities and Deferred Revenue, Current		20,872
Other Liabilities and Deferred Revenue, Noncurrent		24,571
Retained Earnings (Accumulated Deficit)	$ 23,226	22,681	22,668
Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other assets			3,930
Other assets			7,929
Deferred Tax Liabilities, Net			10,412
Other Liabilities and Deferred Revenue, Current			20,556
Other Liabilities and Deferred Revenue, Noncurrent			23,588
Retained Earnings (Accumulated Deficit)			$ 22,668
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other assets		(8)
Other assets		1,324
Deferred Tax Liabilities, Net		(4)
Other Liabilities and Deferred Revenue, Current		316
Other Liabilities and Deferred Revenue, Noncurrent		983
Retained Earnings (Accumulated Deficit)		$ 13