Variable Interest Entities - Consolidataed Balance Sheet (Details) - USD ($) $ in Millions	Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Assets
Cash and cash equivalents	$ 528		$ 580
Short-term investments	18		17
Accounts receivable	880		908
Inventory, net	146		142
Other current assets	36		34
Assets held for sale	0		54
Licenses	2,469		2,186
Property, plant and equipment, net	2,154		2,202
Operating lease right-of-use assets	888	$ 899	0
Other assets and deferred charges	527	567	579
Liabilities
Current liabilities	747		691
Liabilities held for sale	0		1
Long-term operating lease liabilities	858	$ 878	0
Consolidated Variable Interest Entities
Assets
Cash and cash equivalents	8		9
Short-term investments	18		17
Accounts receivable	618		611
Inventory, net	4		5
Other current assets	5		6
Assets held for sale	0		4
Licenses	649		652
Property, plant and equipment, net	91		94
Operating lease right-of-use assets	42		0
Other assets and deferred charges	322		349
Total assets	1,757		1,747
Liabilities
Current liabilities	35		34
Liabilities held for sale	0		1
Long-term operating lease liabilities	38		0
Other deferred liabilities and credits	12		16
Total liabilities	$ 85		$ 51