CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	9 Months Ended
	Dec. 31, 2019	Mar. 31, 2019
Statement of Financial Position [Abstract]
Document Period End Date	Dec. 31, 2019
Operating Lease, Liability, Current	$ 1,860
Current Assets
Cash and Cash Equivalents	3,179	$ 6,982
Short-term Investments	62	67
Accounts and notes receivable, net	3,873	3,554
Device and accessory inventory	1,117	999
Prepaid expenses and other current assets	1,224	1,289
Total current assets	9,455	12,891
Property, plant and equipment, net	20,827	21,201
Costs to acquire a customer contract	1,808	1,559
Operating Lease, Right-of-Use Asset	6,713
Intangible assets
Goodwill	4,598	4,598
FCC licenses and other	41,492	41,465
Property, plant and equipment	918	1,769
Other assets	1,091	1,118
Total assets	86,902	84,601
Current Liabilities
Accounts payable	3,396	3,961
Accrued expenses and other current liabilities	3,335	3,597
Current portion of long-term debt, financing and capital lease obligations	3,880	4,557
Total current liabilities	12,471	12,115
Long-term debt, financing and capital lease obligations	33,507	35,366
Operating Lease, Liability, Noncurrent	5,423
Deferred tax liabilities	7,038	7,556
Other liabilities	2,708	3,437
Total liabilities	61,147	58,474
Commitments and contingencies
Shareholders' Equity
Common stock, voting, par value $0.01 per share, 9.0 billion authorized, 4.013 billion and 4.005 billion issued, respectively	41	41
Paid-in capital	28,402	28,306
Treasury shares, at cost	9	0
Accumulated deficit	(2,226)	(1,883)
Accumulated other comprehensive loss	(453)	(392)
Total stockholders' equity	25,755	26,072
Stockholders' Equity Attributable to Noncontrolling Interest	0	55
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	25,755	26,127
Liabilities and Equity	$ 86,902	$ 84,601