Tower Obligations - Sale Leaseback Transaction (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Leases [Abstract]
Property and equipment, net	$ 329	$ 402
Long-term financial obligation	$ 2,557	$ 2,590

The net book value of the asset(s) sold in connection with the sale of the property to another party and lease back to the seller.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 55
-Paragraph 51
-URI http://asc.fasb.org/extlink&oid=82846721&loc=d3e51840-112757

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 40
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=77888430&loc=SL77919786-209982

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 55
-Paragraph 52
-URI http://asc.fasb.org/extlink&oid=82846721&loc=d3e51843-112757

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 40
-Section 55
-Paragraph 50
-URI http://asc.fasb.org/extlink&oid=82846721&loc=d3e51831-112757

Name:	us-gaap_SaleLeasebackTransactionNetBookValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant