Variable Interest Entities - Consolidated Balance Sheet (Details) - USD ($) $ in Millions	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Assets
Cash and cash equivalents	$ 834		$ 921
Short-term investments	18		17
Accounts receivable	969		992
Inventory, net	154		150
Other current assets	28		28
Licenses	2,478		2,195
Property, plant and equipment, net	3,318		3,346
Operating lease right-of-use assets	963	$ 975	0
Other assets and deferred charges	568	604	616
Liabilities
Current liabilities	925		879
Long-term operating lease liabilities	927	$ 949	0
Consolidated Variable Interest Entities
Assets
Cash and cash equivalents	8		9
Short-term investments	18		17
Accounts receivable	616		609
Inventory, net	4		5
Other current assets	5		5
Licenses	647		647
Property, plant and equipment, net	84		88
Operating lease right-of-use assets	40		0
Other assets and deferred charges	322		347
Total assets	1,744		1,727
Liabilities
Current liabilities	32		31
Long-term operating lease liabilities	37		0
Other deferred liabilities and credits	11		15
Total liabilities	$ 80		$ 46