Debt and Other Obligations Schedule of Extinguishment of Long Term Debt (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Extinguishment of Debt [Line Items]
Gain (Loss) on Extinguishment of Debt		$ (32)	$ 0	$ (106)	$ (4)
January 2010 Tower Revenue Notes [Member]
Extinguishment of Debt [Line Items]
Extinguishment of Debt, Amount				1,250
Repayments of Debt	[1]			1,318
Gain (Loss) on Extinguishment of Debt	[2]			(71)
2016 Term Loan A [Member]
Extinguishment of Debt [Line Items]
Extinguishment of Debt, Amount				0
Repayments of Debt				0
Gain (Loss) on Extinguishment of Debt	[2]			(3)
Fixed Rate Securitized Debt August 2010 Tower Revenue Notes 6 [Member]
Extinguishment of Debt [Line Items]
Extinguishment of Debt, Amount				1,000
Repayments of Debt	[1]			1,028
Gain (Loss) on Extinguishment of Debt	[2]			$ (32)

[1] Exclusive of accrued interest

[2] Inclusive of the write off of respective deferred financing costs.