Commitments and Contingencies - Narrative Part 2 (Details)								3 Months Ended				12 Months Ended	135 Months Ended
	Apr. 05, 2018 USD ($)	Oct. 06, 2017 USD ($)	Jun. 05, 2017 USD ($)	May 22, 2017 USD ($)	Oct. 03, 2016	Sep. 23, 2016 USD ($)	Feb. 12, 2015 USD ($)	Mar. 31, 2019 USD ($) item	Mar. 31, 2018 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Loss contingencies
Total investment													$ 21,000,000,000
Dividend paid to DOC							$ 8,250,000,000
General and administrative expenses								$ 186,577,000	$ 161,684,000
Other accrued expenses
Loss contingencies
Claim amount				$ 1,200
Litigation expense										$ 41,000,000
Telemarketing Litigation
Loss contingencies
Period of injunctive relief sought from placing any outbound telemarketing calls to market or promote its goods or services					5 years			5 years
Number of years for which the company will be barred from accepting orders from that independent third-party retailer if the company fails to prove that a particular independent third-party retailer meets the Demonstration Requirements			2 years
Litigation expense										$ 255,000,000		$ 25,000,000
Litigation accrual			$ 280,000,000
Telemarketing Litigation | Other accrued expenses
Loss contingencies
Litigation accrual								$ 280,000,000					280,000,000	$ 280,000,000
Krakauer Action
Loss contingencies
Litigation expense											$ 20,000,000
Krakauer Action | Other accrued expenses
Loss contingencies
Litigation accrual								$ 61,000,000					$ 61,000,000	$ 61,000,000
Do Not Call Litigation
Loss contingencies
Number of telemarketing calls | item								51,119
Litigation per call damages								$ 400
Turner Network Sales
Loss contingencies
Claim amount		$ 183,000,000
Telemarketing Litigation
Loss contingencies
Judgment in favor of the court	$ 61,000,000
AWS 3 Auction | Northstar Wireless or Northstar Spectrum | Vermont National Telephone Company
Loss contingencies
Bidding Credit						$ 3,300,000,000
Loss Contingency Recovery Amount						10,000,000,000
AWS 3 Auction | Maximum | Northstar Wireless or Northstar Spectrum | Vermont National Telephone Company
Loss contingencies
Claim amount						11,000
AWS 3 Auction | Minimum | Northstar Wireless or Northstar Spectrum | Vermont National Telephone Company
Loss contingencies
Claim amount						$ 5,500