Variable Interest Entities, Consolidated Balance Sheet (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Assets
Cash and cash equivalents	$ 509	$ 352
Accounts receivable	789	775
Other current assets	32	21
Licenses	2,231	2,223
Property, plant and equipment, net	2,233	2,320
Other assets and deferred charges	537	390
Liabilities
Current liabilities	616	733
Consolidated Variable Interest Entities
Assets
Cash and cash equivalents	1	3
Accounts receivable	543	476
Other current assets	8	8
Licenses	654	655
Property, plant and equipment, net	96	99
Other assets and deferred charges	321	303
Total assets	1,623	1,544
Liabilities
Current liabilities	32	39
Deferred liabilities and credits	14	13
Total liabilities	$ 46	$ 52