Repurchases of Common Stock - Narrative (Details) - USD ($)	3 Months Ended	9 Months Ended	21 Months Ended
	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2019	Apr. 27, 2018	Dec. 06, 2017
Affiliated Entity | Deutsche Telekom AG
Equity, Class of Treasury Stock [Line Items]
Additional shares purchased (in shares)	3,300,000	0	0
Aggregate market value of shares purchased	$ 200,000,000
2017 Stock Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, authorized amount				$ 9,000,000,000.0	$ 1,500,000,000
2018 Stock Repurchase Program
Equity, Class of Treasury Stock [Line Items]
Stock repurchase program, increase in authorized amount				$ 7,500,000,000