Accounting Policies - Accounting Pronouncements Recently Adopted (Details) - USD ($) $ in Millions	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Leases, Asset	$ 20,132		$ 0
Operating Lease, Liability	20,881
Accounting Standards Update 2016-02 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Leases, Asset		$ 21,000
Operating Lease, Liability		(21,000)
Financing Obligations Reclassified to Operating Leases		$ 1,200	1,500
Financing Obligations and Construction Liabilities			9,600
Build-to-suit liabilities derecognized			1,500
Financing Obligations Reclassified to Finance Leases			$ 5,400
Accounting Standards Update 2019-02 [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Incremental Capitalized Film Costs	$ 130