Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Accounting policy disclosures
Capitalized Contract Cost	$ 67	$ 51	$ 159	$ 141
Amortization expense related to the programs	21	9	52	17
Total costs capitalized	276		$ 276		$ 169
Revenue, Practical Expedient, Financing Component [true false]			true
Research and Development
Research and development cost	$ 4	$ 6	$ 15	$ 18
Leases
Option to extend - Operating			true
Option to extend - Finance			true
Option to terminate period - Operating			1 year
Option to terminate period - Finance			1 year
Option to terminate - Operating			true
Option to terminate - Finance			true
Minimum
Leases
Option to extend period - Operating	1 year		1 year
Option to extend period - Finance	1 year		1 year
Maximum
Leases
Option to extend period - Operating	8 years		8 years
Option to extend period - Finance	8 years		8 years
Northstar Manager LLC | Minimum
Variable Interest Entity
Number of years after wireless spectrum license is granted until put right vests			5 years
Northstar Manager LLC | Maximum
Variable Interest Entity
Number of years after wireless spectrum license is granted until put right vests			6 years
SNR Wireless Management LLC | Minimum
Variable Interest Entity
Number of years after wireless spectrum license is granted until put right vests			5 years
SNR Wireless Management LLC | Maximum
Variable Interest Entity
Number of years after wireless spectrum license is granted until put right vests			6 years