Guarantor Financial Information CONDENSED CONSOLIDATING BALANCE SHEET (Details) (Successor [Member], USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Mar. 31, 2014	Sep. 30, 2013	Mar. 31, 2013
Current Assets
Cash and cash equivalents, beginning of period	$ 4,135	$ 4,970	$ 6,058	$ 3
Short-term Investments	1,167	1,220
Accounts and notes receivable, net	3,942	3,607
Device and accessory inventory	1,124	982
Current deferred tax asset	90	128
Prepaid expenses and other current assets	812	672
Total current assets	11,270	11,579
Investments	153	146
Investments in Subsidiaries	0	0
Property, plant and equipment, net	17,557	16,299
Due from Affiliate, Noncurrent	0	0
Note receivable from consolidated affiliate	0	0
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	6,343	6,383
FCC licenses and other	41,800	41,978
Definite-lived intangible assets, net	6,696	7,558
Other assets	891	746
Total assets	84,710	84,689
Current Liabilities
Accounts Payable, Current	4,351	3,163
Accrued expenses and other current liabilities	5,439	5,544
Current portion of long-term debt, financing and capital lease obligations	808	991
Total current liabilities	10,598	9,698
Long-term debt, financing and capital lease obligations	31,458	31,787
Deferred tax liabilities	14,331	14,207
Note due to consolidated affiliate	0	0
Other liabilities	3,660	3,685
Due to affiliate	0	0
Total liabilities	60,047	59,377
Commitments and contingencies
Total shareholders' equity	24,663	25,312
Liabilities and Equity	84,710	84,689
Parent Company [Member]
Current Assets
Cash and cash equivalents, beginning of period	0	0	100	3
Short-term Investments	0	0
Accounts and notes receivable, net	73	74
Device and accessory inventory	0	0
Current deferred tax asset	0	0
Prepaid expenses and other current assets	0	0
Total current assets	73	74
Investments	0	0
Investments in Subsidiaries	24,665	25,316
Property, plant and equipment, net	0	0
Due from Affiliate, Noncurrent	0	0
Note receivable from consolidated affiliate	9,000	9,000
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	0	0
FCC licenses and other	0	0
Definite-lived intangible assets, net	0	0
Other assets	126	133
Total assets	33,864	34,523
Current Liabilities
Accounts Payable, Current	0	0
Accrued expenses and other current liabilities	75	78
Current portion of long-term debt, financing and capital lease obligations	0	0
Total current liabilities	75	78
Long-term debt, financing and capital lease obligations	9,000	9,000
Deferred tax liabilities	0	0
Note due to consolidated affiliate	0	0
Other liabilities	0	0
Due to affiliate	126	133
Total liabilities	9,201	9,211
Total shareholders' equity	24,663	25,312
Liabilities and Equity	33,864	34,523
Guarantor Subsidiaries [Member]
Current Assets
Cash and cash equivalents, beginning of period	3,488	4,125	5,208	0
Short-term Investments	1,132	1,220
Accounts and notes receivable, net	67	27
Device and accessory inventory	0	0
Current deferred tax asset	0	0
Prepaid expenses and other current assets	16	14
Total current assets	4,703	5,386
Investments	1,114	1,104
Investments in Subsidiaries	24,983	25,588
Property, plant and equipment, net	0	0
Due from Affiliate, Noncurrent	18,703	18,234
Note receivable from consolidated affiliate	0	0
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	0	0
FCC licenses and other	0	0
Definite-lived intangible assets, net	0	0
Other assets	126	133
Total assets	49,629	50,445
Current Liabilities
Accounts Payable, Current	0	0
Accrued expenses and other current liabilities	482	493
Current portion of long-term debt, financing and capital lease obligations	0	0
Total current liabilities	482	493
Long-term debt, financing and capital lease obligations	14,903	15,027
Deferred tax liabilities	0	0
Note due to consolidated affiliate	9,000	9,000
Other liabilities	579	609
Due to affiliate	0	0
Total liabilities	24,964	25,129
Total shareholders' equity	24,665	25,316
Liabilities and Equity	49,629	50,445
Non-Guarantor Subsidiaries [Member]
Current Assets
Cash and cash equivalents, beginning of period	647	845	750	0
Short-term Investments	35	0
Accounts and notes receivable, net	3,942	3,607
Device and accessory inventory	1,124	982
Current deferred tax asset	90	128
Prepaid expenses and other current assets	796	658
Total current assets	6,634	6,220
Investments	58	61
Investments in Subsidiaries	0	0
Property, plant and equipment, net	17,557	16,299
Due from Affiliate, Noncurrent	0	0
Note receivable from consolidated affiliate	0	0
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	6,343	6,383
FCC licenses and other	41,800	41,978
Definite-lived intangible assets, net	6,696	7,558
Other assets	765	613
Total assets	79,853	79,112
Current Liabilities
Accounts Payable, Current	4,351	3,163
Accrued expenses and other current liabilities	5,022	5,074
Current portion of long-term debt, financing and capital lease obligations	808	991
Total current liabilities	10,181	9,228
Long-term debt, financing and capital lease obligations	8,574	8,779
Deferred tax liabilities	14,331	14,207
Note due to consolidated affiliate	0	0
Other liabilities	3,081	3,076
Due to affiliate	18,703	18,234
Total liabilities	54,870	53,524
Total shareholders' equity	24,983	25,588
Liabilities and Equity	79,853	79,112
Consolidation, Eliminations [Member]
Current Assets
Cash and cash equivalents, beginning of period	0	0	0	0
Short-term Investments	0	0
Accounts and notes receivable, net	(140)	(101)
Device and accessory inventory	0	0
Current deferred tax asset	0	0
Prepaid expenses and other current assets	0	0
Total current assets	(140)	(101)
Investments	(1,019)	(1,019)
Investments in Subsidiaries	(49,648)	(50,904)
Property, plant and equipment, net	0	0
Due from Affiliate, Noncurrent	(18,703)	(18,234)
Note receivable from consolidated affiliate	(9,000)	(9,000)
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	0	0
FCC licenses and other	0	0
Definite-lived intangible assets, net	0	0
Other assets	(126)	(133)
Total assets	(78,636)	(79,391)
Current Liabilities
Accounts Payable, Current	0	0
Accrued expenses and other current liabilities	(140)	(101)
Current portion of long-term debt, financing and capital lease obligations	0	0
Total current liabilities	(140)	(101)
Long-term debt, financing and capital lease obligations	(1,019)	(1,019)
Deferred tax liabilities	0	0
Note due to consolidated affiliate	(9,000)	(9,000)
Other liabilities	0	0
Due to affiliate	(18,829)	(18,367)
Total liabilities	(28,988)	(28,487)
Total shareholders' equity	(49,648)	(50,904)
Liabilities and Equity	$ (78,636)	$ (79,391)