Guarantor Financial Information (CONDENSED CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (LOSS)) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Condensed Income Statements, Captions [Line Items]
Net Income (Loss) Attributable to Parent	$ 196,000	$ (48,000)	$ 372,000	$ 158,000
Net operating revenues	8,433,000	7,927,000	16,558,000	16,084,000
Service revenue	8,433,000		16,558,000
Revenue, equipment sales, net	1,418,000	994,000	2,591,000	2,181,000
Revenue, equipment rentals, net	1,253,000	966,000	2,465,000	1,865,000
Cost of Services (exclusive of depreciation and amortization included below)	1,694,000	1,698,000	3,371,000	3,407,000
Cost of equipment sales	1,517,000	1,404,000	2,787,000	2,949,000
Cost of equipment rentals	151,000	112,000	275,000	224,000
Net operating expenses
Selling, general and administrative	1,861,000	2,013,000	3,728,000	3,951,000
Severance and exit costs	25,000	0	33,000	0
Depreciation, network and other	1,021,000	997,000	2,044,000	1,974,000
Depreciation, equipment rentals	1,181,000	888,000	2,317,000	1,742,000
Amortization	159,000	209,000	330,000	432,000
Other, net	46,000	5,000	80,000	(359,000)
Total costs and expenses	7,655,000	7,326,000	14,965,000	14,320,000
Operating Income	778,000	601,000	1,593,000	1,764,000
Other (expense) income
Interest Income	49,000	33,000	91,000	52,000
Interest Expense	(633,000)	(595,000)	(1,270,000)	(1,208,000)
Equity in earnings (losses) of unconsolidated subsidiary	0		0
(Losses) earnings of Subsidiaries	0	0	0	0
Realized Investment Gains (Losses)	0		0
Other nonoperating income (expense), excluding interest income	30,000	11,000	30,000	(60,000)
Nonoperating Expense	(554,000)	(551,000)	(1,149,000)	(1,216,000)
Loss (income) before income taxes	224,000	50,000	444,000	548,000
Income tax benefit	(17,000)	(98,000)	(64,000)	(390,000)
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	207,000	(48,000)	380,000	158,000
Net Income (Loss) Attributable to Noncontrolling Interest	11,000	0	8,000	0
Other Comprehensive Income (Loss), Net of Tax	9,000	16,000	5,000	12,000
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	216,000		385,000	170,000
Comprehensive (loss) income	216,000	(32,000)	385,000	170,000
Consolidation, Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Net Income (Loss) Attributable to Parent	(463,000)	(62,000)	(841,000)
Net operating revenues	0	0	0	0
Revenue, equipment sales, net	0	0	0	0
Revenue, equipment rentals, net	0	0	0	0
Cost of Services (exclusive of depreciation and amortization included below)	0	0	0	0
Cost of equipment sales	0	0	0	0
Cost of equipment rentals	0	0	0	0
Net operating expenses
Selling, general and administrative	0	0	0	0
Severance and exit costs	0		0
Depreciation, network and other	0	0	0	0
Depreciation, equipment rentals	0	0	0	0
Amortization	0	0	0	0
Other, net	0	0	0	0
Total costs and expenses	0	0	0	0
Operating Income	0	0	0	0
Other (expense) income
Interest Income	(1,062,000)	(449,000)	(1,795,000)	(677,000)
Interest Expense	1,062,000	449,000	1,795,000	677,000
Equity in earnings (losses) of unconsolidated subsidiary	0		0
(Losses) earnings of Subsidiaries	(463,000)	(62,000)	(841,000)	(792,000)
Realized Investment Gains (Losses)	0		0
Other nonoperating income (expense), excluding interest income	0	0	0	0
Nonoperating Expense	(463,000)	(62,000)	(841,000)	(792,000)
Loss (income) before income taxes	(463,000)	(62,000)	(841,000)	(792,000)
Income tax benefit	0	0	0	0
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	(463,000)		(841,000)	(792,000)
Net Income (Loss) Attributable to Noncontrolling Interest	0		0
Other Comprehensive Income (Loss), Net of Tax	(12,000)	(23,000)	5,000	(24,000)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	(475,000)		(836,000)	(816,000)
Comprehensive (loss) income		(85,000)
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Net Income (Loss) Attributable to Parent	196,000	(48,000)	372,000
Net operating revenues	0	0	0	0
Revenue, equipment sales, net	0	0	0	0
Revenue, equipment rentals, net	0	0	0	0
Cost of Services (exclusive of depreciation and amortization included below)	0	0	0	0
Cost of equipment sales	0	0	0	0
Cost of equipment rentals	0	0	0	0
Net operating expenses
Selling, general and administrative	0	0	0	0
Severance and exit costs	0		0
Depreciation, network and other	0	0	0	0
Depreciation, equipment rentals	0	0	0	0
Amortization	0	0	0	0
Other, net	0	0	0	0
Total costs and expenses	0	0	0	0
Operating Income	0	0	0	0
Other (expense) income
Interest Income	226,000	197,000	452,000	395,000
Interest Expense	(226,000)	(197,000)	(452,000)	(395,000)
Equity in earnings (losses) of unconsolidated subsidiary	0		0
(Losses) earnings of Subsidiaries	196,000	(48,000)	372,000	158,000
Realized Investment Gains (Losses)	0		0
Other nonoperating income (expense), excluding interest income	0	0	0	0
Nonoperating Expense	196,000	(48,000)	372,000	158,000
Loss (income) before income taxes	196,000	(48,000)	372,000	158,000
Income tax benefit	0	0	0	0
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	196,000		372,000	158,000
Net Income (Loss) Attributable to Noncontrolling Interest	0		0
Other Comprehensive Income (Loss), Net of Tax	9,000	16,000	5,000	12,000
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	205,000		377,000	170,000
Comprehensive (loss) income		(32,000)
Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Net Income (Loss) Attributable to Parent	196,000	(48,000)	372,000
Net operating revenues	0	0	0	0
Revenue, equipment sales, net	0	0	0	0
Revenue, equipment rentals, net	0	0	0	0
Cost of Services (exclusive of depreciation and amortization included below)	0	0	0	0
Cost of equipment sales	0	0	0	0
Cost of equipment rentals	0	0	0	0
Net operating expenses
Selling, general and administrative	0	0	0	0
Severance and exit costs	0		0
Depreciation, network and other	0	0	0	0
Depreciation, equipment rentals	0	0	0	0
Amortization	0	0	0	0
Other, net	0	0	0	(55,000)
Total costs and expenses	0	0	0	(55,000)
Operating Income	0	0	0	55,000
Other (expense) income
Interest Income	545,000	280,000	1,092,000	325,000
Interest Expense	(638,000)	(438,000)	(1,209,000)	(789,000)
Equity in earnings (losses) of unconsolidated subsidiary	0		0
(Losses) earnings of Subsidiaries	267,000	110,000	469,000	634,000
Realized Investment Gains (Losses)	0		0
Other nonoperating income (expense), excluding interest income	22,000	0	20,000	(67,000)
Nonoperating Expense	196,000	(48,000)	372,000	103,000
Loss (income) before income taxes	196,000	(48,000)	372,000	158,000
Income tax benefit	0	0	0	0
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	196,000		372,000	158,000
Net Income (Loss) Attributable to Noncontrolling Interest	0		0
Other Comprehensive Income (Loss), Net of Tax	9,000	16,000	5,000	12,000
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	205,000		377,000	170,000
Comprehensive (loss) income		(32,000)
Non-Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Net Income (Loss) Attributable to Parent	267,000	110,000	469,000
Net operating revenues	8,433,000	7,927,000	16,558,000	16,084,000
Revenue, equipment sales, net	1,418,000	994,000	2,591,000	2,181,000
Revenue, equipment rentals, net	1,253,000	966,000	2,465,000	1,865,000
Cost of Services (exclusive of depreciation and amortization included below)	1,694,000	1,698,000	3,371,000	3,407,000
Cost of equipment sales	1,517,000	1,404,000	2,787,000	2,949,000
Cost of equipment rentals	151,000	112,000	275,000	224,000
Net operating expenses
Selling, general and administrative	1,861,000	2,013,000	3,728,000	3,951,000
Severance and exit costs	25,000		33,000
Depreciation, network and other	1,021,000	997,000	2,044,000	1,974,000
Depreciation, equipment rentals	1,181,000	888,000	2,317,000	1,742,000
Amortization	159,000	209,000	330,000	432,000
Other, net	46,000	5,000	80,000	(304,000)
Total costs and expenses	7,655,000	7,326,000	14,965,000	14,375,000
Operating Income	778,000	601,000	1,593,000	1,709,000
Other (expense) income
Interest Income	340,000	5,000	342,000	9,000
Interest Expense	(831,000)	(409,000)	(1,404,000)	(701,000)
Equity in earnings (losses) of unconsolidated subsidiary	0		0
(Losses) earnings of Subsidiaries	0	0	0	0
Realized Investment Gains (Losses)	0		0
Other nonoperating income (expense), excluding interest income	8,000	11,000	10,000	7,000
Nonoperating Expense	(483,000)	(393,000)	(1,052,000)	(685,000)
Loss (income) before income taxes	295,000	208,000	541,000	1,024,000
Income tax benefit	(17,000)	(98,000)	(64,000)	(390,000)
Income (Loss) from Continuing Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest	278,000		477,000	634,000
Net Income (Loss) Attributable to Noncontrolling Interest	11,000		8,000
Other Comprehensive Income (Loss), Net of Tax	3,000	7,000	(10,000)	12,000
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	281,000		467,000	646,000
Comprehensive (loss) income		117,000
Services [Member]
Condensed Income Statements, Captions [Line Items]
Service revenue	5,762,000	5,967,000	11,502,000	12,038,000
Services [Member] | Consolidation, Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Service revenue	0	0	0	0
Services [Member] | Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Service revenue	0	0	0	0
Services [Member] | Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Service revenue	0	0	0	0
Services [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Service revenue	$ 5,762,000	$ 5,967,000	$ 11,502,000	$ 12,038,000