Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Commitment And Contingencies [Line Items]
Operating lease expense inclusive of short-term and variable lease expenses	$ 264		$ 538
Weighted average remaining lease term for operating leases	10 years		10 years
Weighted average discount rate used to calculate operating lease liabilities	3.85%		3.85%
Cash payments for operating leases			$ 446
Rental expense		$ 184		$ 370
Redeemable Subsidiary Preferred Stock [Member] | Level 2 [Member]
Commitment And Contingencies [Line Items]
Temporary equity, fair value of redeemable subsidiary preferred stock	$ 744		$ 744
Sky Limited [Member]
Commitment And Contingencies [Line Items]
Future cash payments related to additional contracts determined to be operating leases					$ 804