CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Millions	3 Months Ended								12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Revenues [Abstract]
Service									$ 22,857,000,000	$ 23,834,000,000	$ 25,368,000,000
Revenue, equipment sales, net									5,606,000,000	4,524,000,000	4,684,000,000
Revenue, equipment rentals, net									5,137,000,000	4,048,000,000	3,295,000,000
Inter-segment revenues	$ 8,441,000,000	$ 8,601,000,000	$ 8,433,000,000	$ 8,125,000,000	$ 8,083,000,000	$ 8,239,000,000	$ 7,927,000,000	$ 8,157,000,000	33,600,000,000	32,406,000,000	33,347,000,000
Net operating expenses:
Cost of services (exclusive of depreciation and amortization included below)									6,664,000,000	6,801,000,000	7,861,000,000
Cost of equipment rentals									643,000,000	493,000,000	975,000,000
Cost of equipment sales									6,082,000,000	6,109,000,000	6,583,000,000
Selling, general and administrative									7,774,000,000	8,087,000,000	7,994,000,000
Impairments									2,000,000,000	0	0
Depreciation, equipment rentals									4,538,000,000	3,792,000,000	3,116,000,000
Depreciation, network and other									4,245,000,000	3,976,000,000	3,982,000,000
Amortization									608,000,000	812,000,000	1,052,000,000
Goodwill, Impairment Loss									2,000,000,000
Other Operating Income (Expense), Net									(648,000,000)	(391,000,000)	20,000,000
Total costs and expenses									33,202,000,000	29,679,000,000	31,583,000,000
Operating (loss) income	(1,674,000,000)	479,000,000	778,000,000	815,000,000	236,000,000	727,000,000	601,000,000	1,163,000,000	398,000,000	2,727,000,000	1,764,000,000
Other (expense) income:
Interest expense									(2,563,000,000)	(2,365,000,000)	(2,495,000,000)
Other income (expense), net									187,000,000	(59,000,000)	(40,000,000)
Nonoperating income (expense)									(2,376,000,000)	(2,424,000,000)	(2,535,000,000)
Income (loss) before income taxes									(1,978,000,000)	303,000,000	(771,000,000)
Income tax benefit (expense)									35,000,000	7,074,000,000	(435,000,000)
Net loss	$ (2,174)	$ (141)	$ 196	$ 176	$ 0	$ 0	$ 0	$ 0	(1,943,000,000)	7,389,000,000	(1,206,000,000)
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest									(1,943,000,000)	7,377,000,000	(1,206,000,000)
Net Income (Loss) Attributable to Noncontrolling Interest									$ 0	$ 12,000,000	$ 0
Earnings Per Share, Basic	$ (0.53)	$ (0.03)	$ 0.05	$ 0.04	$ 0.02	$ 1.79	$ (0.01)	$ 0.05	$ (0.48)	$ 1.85	$ (0.30)
Earnings Per Share, Diluted	$ (530,000)	$ (30,000)	$ 50,000	$ 40,000	$ 20,000	$ 1,760,000	$ (10,000)	$ 50,000	$ (0.48)	$ 1.81	$ (0.30)
Weighted Average Number of Shares Outstanding, Basic									4,057	3,999	3,981
Weighted Average Number of Shares Outstanding, Diluted									4,057	4,078	3,981