Variable Interest Entities - Consolidated Balance Sheet (Details) - USD ($) $ in Millions	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Assets
Cash and cash equivalents	$ 853		$ 921
Short-term investments	0		17
Accounts receivable	989		992
Inventory, net	147		150
Other current assets	28		28
Licenses	2,470		2,195
Property, plant and equipment, net	3,353		3,346
Operating lease right-of-use assets	970	$ 975	0
Other assets and deferred charges	579	604	616
Liabilities
Current liabilities	1,001		879
Long-term operating lease liabilities	931	$ 949	0
Consolidated Variable Interest Entities
Assets
Cash and cash equivalents	29		9
Short-term investments	0		17
Accounts receivable	623		609
Inventory, net	4		5
Other current assets	6		5
Licenses	647		647
Property, plant and equipment, net	87		88
Operating lease right-of-use assets	41		0
Other assets and deferred charges	327		347
Total assets	1,764		1,727
Liabilities
Current liabilities	32		31
Long-term operating lease liabilities	37		0
Other deferred liabilities and credits	12		15
Total liabilities	$ 81		$ 46