Debt and Other Obligations Contractual Maturities (Details) - USD ($) $ in Millions		Jun. 30, 2021		Dec. 31, 2020
Contractual Obligation, Fiscal Year Maturity Schedule [Abstract]
Long-Term Debt, Maturity, remaining six months	[1],[2]	$ 113
Long-Term Debt, Maturity, Year Two	[1]	71
Long-Term Debt, Maturity, Year Three	[1]	1,838
Long-Term Debt, Maturity, Year Four	[1]	842
Long-Term Debt, Maturity, Year Five	[1]	635
Long-Term Debt, Maturity, after Year Five	[1]	16,767
Total Cash Obligations	[1]	20,266
Unamortized Adjustments, Net	[1]	(181)
Debt and Finance Lease Obligations		$ 20,085	[1]	$ 19,280

[1] Inclusive of the previously outstanding Tower Revenue Notes, Series 2015-1, which were repaid in July 2021. See note 12 for further discussion regarding the July repayment of previously outstanding debt.

[2] Predominately consists of outstanding indebtedness under the CP Program. Such amounts may be issued, repaid or re-issued from time to time.