Commitments and Contingencies - Part 2 (Details) person in Millions						3 Months Ended	12 Months Ended
	Sep. 29, 2023 person	Sep. 23, 2016 USD ($)	Aug. 18, 2015 USD ($)	Jul. 17, 2015 USD ($)	Mar. 14, 2014 USD ($)	Mar. 31, 2024 USD ($) item	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Loss contingencies
Number of Americans Nationwide For Deploy FiveG Services | person	200
Wireless
Loss contingencies
Network development current and future expenditures						$ 10,000,000,000	$ 10,000,000,000	$ 10,000,000,000	$ 10,000,000,000
Northstar Spectrum And SNR Holdco | AWS-3 Licenses
Loss contingency terms
Percentage of bidding credit						25.00%
Northstar Wireless or Northstar Spectrum | AWS-3 Licenses | Vermont National Telephone Company
Loss contingency terms
Percentage of bidding credit		25.00%
Recovery amount		$ 10,000,000,000
Bidding credit value		3,300,000,000
Northstar Wireless or Northstar Spectrum | AWS-3 Licenses | Minimum | Vermont National Telephone Company
Loss contingency terms
Claim amount		5,500
Northstar Wireless or Northstar Spectrum | AWS-3 Licenses | Maximum | Vermont National Telephone Company
Loss contingency terms
Claim amount		$ 11,000
Northstar Wireless or Northstar Spectrum | SNR Licenses
Loss contingency terms
Percentage of bidding credit			25.00%
Northstar Wireless or Northstar Spectrum | Northstar Licenses
Loss contingency terms
Bidding credit value			$ 1,961,000,000
SNR Wireless or SNR Wireless Holdco | SNR Licenses
Loss contingency terms
Bidding credit value			$ 1,370,000,000
Pending Litigation | ClearPlay
Loss contingency terms
Claim amount					$ 469,000,000
Pending Litigation | TQ Delta
Loss contingency terms
Claim amount				$ 251,000,000
Cyber-Security Class Actions
Loss contingency terms
Ten additional putative class action complaints | item						10