Guarantor Financial Information (CONDENSED CONSOLIDATING BALANCE SHEET) (Details) - USD ($) $ in Millions	Jun. 30, 2015	Mar. 31, 2015
Current Assets
Short-term Investments	$ 203	$ 166
Accounts and notes receivable, net	3,813	2,290
Device and accessory inventory	949	1,359
Current deferred tax asset	87	62
Prepaid expenses and other current assets	673	1,890
Total current assets	7,785	9,777
Investments in Subsidiaries	0	0
Property, plant and equipment, net	20,563	19,721
Due from Affiliate, Noncurrent	0	0
Note receivable from consolidated affiliate	0	0
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	6,575	6,575
FCC licenses and other	40,013	39,987
Definite-lived intangible assets, net	5,516	5,893
Other assets	987	1,077
Total assets	81,439	83,030
Current Liabilities
Accounts Payable, Current	3,272	4,347
Accrued expenses and other current liabilities	4,458	5,293
Current portion of long-term debt, financing and capital lease obligations	1,384	1,300
Total current liabilities	9,114	10,940
Long-term debt, financing and capital lease obligations	32,746	32,531
Deferred tax liabilities	13,913	13,898
Note due to consolidated affiliate	0	0
Other liabilities	3,941	3,951
Due to affiliate	0	0
Total liabilities	$ 59,714	$ 61,320
Commitments and contingencies
Total stockholders' equity	$ 21,725	$ 21,710
Liabilities and Equity	81,439	83,030
Parent Company [Member]
Current Assets
Short-term Investments	0	0
Accounts and notes receivable, net	193	84
Device and accessory inventory	0	0
Current deferred tax asset	0	0
Prepaid expenses and other current assets	0	0
Total current assets	193	84
Investments in Subsidiaries	21,727	21,712
Property, plant and equipment, net	0	0
Due from Affiliate, Noncurrent	68	68
Note receivable from consolidated affiliate	10,500	10,500
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	0	0
FCC licenses and other	0	0
Definite-lived intangible assets, net	0	0
Other assets	135	139
Total assets	32,623	32,503
Current Liabilities
Accounts Payable, Current	0	0
Accrued expenses and other current liabilities	263	154
Current portion of long-term debt, financing and capital lease obligations	0	0
Total current liabilities	263	154
Long-term debt, financing and capital lease obligations	10,500	10,500
Deferred tax liabilities	0	0
Note due to consolidated affiliate	0	0
Other liabilities	0	0
Due to affiliate	135	139
Total liabilities	10,898	10,793
Total stockholders' equity	21,725	21,710
Liabilities and Equity	32,623	32,503
Guarantor Subsidiaries [Member]
Current Assets
Short-term Investments	163	146
Accounts and notes receivable, net	177	157
Device and accessory inventory	0	0
Current deferred tax asset	0	0
Prepaid expenses and other current assets	17	13
Total current assets	1,878	3,808
Investments in Subsidiaries	22,778	22,413
Property, plant and equipment, net	0	0
Due from Affiliate, Noncurrent	22,434	20,934
Note receivable from consolidated affiliate	513	458
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	0	0
FCC licenses and other	0	0
Definite-lived intangible assets, net	0	0
Other assets	1,259	1,260
Total assets	48,862	48,873
Current Liabilities
Accounts Payable, Current	0	0
Accrued expenses and other current liabilities	669	625
Current portion of long-term debt, financing and capital lease obligations	500	500
Total current liabilities	1,169	1,125
Long-term debt, financing and capital lease obligations	14,511	14,576
Deferred tax liabilities	0	0
Note due to consolidated affiliate	10,500	10,500
Other liabilities	955	960
Due to affiliate	0	0
Total liabilities	27,135	27,161
Total stockholders' equity	21,727	21,712
Liabilities and Equity	48,862	48,873
Non-Guarantor Subsidiaries [Member]
Current Assets
Short-term Investments	40	20
Accounts and notes receivable, net	3,683	2,160
Device and accessory inventory	949	1,359
Current deferred tax asset	87	62
Prepaid expenses and other current assets	656	1,877
Total current assets	5,954	5,996
Investments in Subsidiaries	0	0
Property, plant and equipment, net	20,563	19,721
Due from Affiliate, Noncurrent	0	0
Note receivable from consolidated affiliate	0	0
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	6,575	6,575
FCC licenses and other	40,013	39,987
Definite-lived intangible assets, net	5,516	5,893
Other assets	747	836
Total assets	79,368	79,008
Current Liabilities
Accounts Payable, Current	3,272	4,347
Accrued expenses and other current liabilities	3,766	4,625
Current portion of long-term debt, financing and capital lease obligations	884	800
Total current liabilities	7,922	9,772
Long-term debt, financing and capital lease obligations	8,754	8,474
Deferred tax liabilities	13,913	13,898
Note due to consolidated affiliate	513	458
Other liabilities	2,986	2,991
Due to affiliate	22,502	21,002
Total liabilities	56,590	56,595
Total stockholders' equity	22,778	22,413
Liabilities and Equity	79,368	79,008
Consolidation, Eliminations [Member]
Current Assets
Short-term Investments	0	0
Accounts and notes receivable, net	(240)	(111)
Device and accessory inventory	0	0
Current deferred tax asset	0	0
Prepaid expenses and other current assets	0	0
Total current assets	(240)	(111)
Investments in Subsidiaries	(44,505)	(44,125)
Property, plant and equipment, net	0	0
Due from Affiliate, Noncurrent	(22,502)	(21,002)
Note receivable from consolidated affiliate	(11,013)	(10,958)
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	0	0
FCC licenses and other	0	0
Definite-lived intangible assets, net	0	0
Other assets	(1,154)	(1,158)
Total assets	(79,414)	(77,354)
Current Liabilities
Accounts Payable, Current	0	0
Accrued expenses and other current liabilities	(240)	(111)
Current portion of long-term debt, financing and capital lease obligations	0	0
Total current liabilities	(240)	(111)
Long-term debt, financing and capital lease obligations	(1,019)	(1,019)
Deferred tax liabilities	0	0
Note due to consolidated affiliate	(11,013)	(10,958)
Other liabilities	0	0
Due to affiliate	(22,637)	(21,141)
Total liabilities	(34,909)	(33,229)
Total stockholders' equity	(44,505)	(44,125)
Liabilities and Equity	$ (79,414)	$ (77,354)