Guarantor Financial Information (CONDENSED CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (LOSS)) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Condensed Income Statements, Captions [Line Items]
Net operating revenues	$ 8,549	$ 8,107	$ 24,808	$ 24,109
Cost of Services (exclusive of depreciation and amortization included below)	1,925	2,348	6,125	7,194
Cost of Products (exclusive of depreciation and amortization included below)	1,985	1,589	5,097	4,244
Net operating expenses
Selling, general and administrative	2,080	2,129	5,992	6,540
Severance and exit costs	19	209	30	247
Depreciation	1,837	1,549	5,227	4,202
Amortization	255	316	813	994
Other, net	137	164	230	386
Total costs and expenses	8,238	8,304	23,514	23,807
Operating Income	311	(197)	1,294	302
Other (expense) income
Interest Income	12	3	37	7
Interest Expense	(619)	(546)	(1,864)	(1,630)
(Losses) earnings of Subsidiaries	0	0	0	0
Other nonoperating income (expense), excluding interest income	(72)	1	(104)	6
Nonoperating Expense	(679)	(542)	(1,931)	(1,617)
Loss (income) before income taxes	(368)	(739)	(637)	(1,315)
Income tax benefit	(111)	(97)	(286)	(126)
Net (loss) income	(479)	(836)	(923)	(1,441)
Other Comprehensive Income (Loss), Net of Tax	(5)	(7)	2	(11)
Comprehensive (loss) income	(484)	(843)	(921)	(1,452)
Consolidation, Eliminations [Member]
Condensed Income Statements, Captions [Line Items]
Net operating revenues	0	0	0	0
Cost of Services (exclusive of depreciation and amortization included below)	0	0	0	0
Cost of Products (exclusive of depreciation and amortization included below)	0	0	0	0
Net operating expenses
Selling, general and administrative	0	0	0	0
Severance and exit costs	0	0	0	0
Depreciation	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	(233)	(236)	(674)	(707)
Interest Expense	233	236	674	707
(Losses) earnings of Subsidiaries	517	1,309	603	1,784
Other nonoperating income (expense), excluding interest income	0	0	0	0
Nonoperating Expense	517	1,309	603	1,784
Loss (income) before income taxes	517	1,309	603	1,784
Income tax benefit	0	0	0	0
Net (loss) income	517	1,309	603	1,784
Other Comprehensive Income (Loss), Net of Tax	9	11	(5)	17
Comprehensive (loss) income	526	1,320	598	1,801
Parent Company [Member]
Condensed Income Statements, Captions [Line Items]
Net operating revenues	0	0	0	0
Cost of Services (exclusive of depreciation and amortization included below)	0	0	0	0
Cost of Products (exclusive of depreciation and amortization included below)	0	0	0	0
Net operating expenses
Selling, general and administrative	0	0	0	0
Severance and exit costs	0	0	0	0
Depreciation	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	198	198	593	593
Interest Expense	(198)	(198)	(593)	(593)
(Losses) earnings of Subsidiaries	(479)	(838)	(923)	(1,443)
Other nonoperating income (expense), excluding interest income	0	0	0	0
Nonoperating Expense	(479)	(838)	(923)	(1,443)
Loss (income) before income taxes	(479)	(838)	(923)	(1,443)
Income tax benefit	0	2	0	2
Net (loss) income	(479)	(836)	(923)	(1,441)
Other Comprehensive Income (Loss), Net of Tax	(5)	(7)	2	(11)
Comprehensive (loss) income	(484)	(843)	(921)	(1,452)
Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Net operating revenues	0	0	0	0
Cost of Services (exclusive of depreciation and amortization included below)	0	0	0	0
Cost of Products (exclusive of depreciation and amortization included below)	0	0	0	0
Net operating expenses
Selling, general and administrative	0	0	0	0
Severance and exit costs	0	0	0	0
Depreciation	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	43	39	105	118
Interest Expense	(409)	(406)	(1,271)	(1,220)
(Losses) earnings of Subsidiaries	(38)	(471)	320	(341)
Other nonoperating income (expense), excluding interest income	(75)	0	(77)	0
Nonoperating Expense	(479)	(838)	(923)	(1,443)
Loss (income) before income taxes	(479)	(838)	(923)	(1,443)
Income tax benefit	0	0	0	0
Net (loss) income	(479)	(838)	(923)	(1,443)
Other Comprehensive Income (Loss), Net of Tax	(5)	(7)	2	(11)
Comprehensive (loss) income	(484)	(845)	(921)	(1,454)
Non-Guarantor Subsidiaries [Member]
Condensed Income Statements, Captions [Line Items]
Net operating revenues	8,549	8,107	24,808	24,109
Cost of Services (exclusive of depreciation and amortization included below)	1,925	2,348	6,125	7,194
Cost of Products (exclusive of depreciation and amortization included below)	1,985	1,589	5,097	4,244
Net operating expenses
Selling, general and administrative	2,080	2,129	5,992	6,540
Severance and exit costs	19	209	30	247
Depreciation	1,837	1,549	5,227	4,202
Amortization	255	316	813	994
Other, net	137	164	230	386
Total costs and expenses	8,238	8,304	23,514	23,807
Operating Income	311	(197)	1,294	302
Other (expense) income
Interest Income	4	2	13	3
Interest Expense	(245)	(178)	(674)	(524)
(Losses) earnings of Subsidiaries	0	0	0	0
Other nonoperating income (expense), excluding interest income	3	1	(27)	6
Nonoperating Expense	(238)	(175)	(688)	(515)
Loss (income) before income taxes	73	(372)	606	(213)
Income tax benefit	(111)	(99)	(286)	(128)
Net (loss) income	(38)	(471)	320	(341)
Other Comprehensive Income (Loss), Net of Tax	(4)	(4)	3	(6)
Comprehensive (loss) income	$ (42)	$ (475)	$ 323	$ (347)