Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Accounting policy disclosures
Capitalized Contract Cost	$ 55	$ 49	$ 92	$ 90
Amortization expense related to the programs	17	5	31	8
Total costs capitalized	230		$ 230		$ 169
Revenue, Practical Expedient, Financing Component [true false]			true
Research and Development
Research and development cost	$ 6	$ 6	$ 11	$ 12
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	12 years		12 years
Option to extend period - Finance	12 years		12 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