Guarantor Financial Information (CONDENSED CONSOLIDATING BALANCE SHEET) (Details) - USD ($) $ in Millions	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014
Current Assets
Cash and Cash Equivalents	$ 3,780	$ 2,641	$ 2,060	$ 4,010	$ 2,060	$ 4,010
Short-term Investments	1,304	0
Accounts and notes receivable, net	1,113	1,099
Device and accessory inventory	816	1,173
Prepaid expenses and other current assets	1,949	1,920
Total current assets	8,962	6,833
Investments in Subsidiaries	0	0
Property, plant and equipment, net	19,715	20,297
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	40,175	40,073
Definite-lived intangible assets, net	4,157	4,469
Other assets	811	728
Total assets	80,395	78,975
Current Liabilities
Accounts Payable, Current	1,841	2,899
Accrued expenses and other current liabilities	4,245	4,374
Current portion of long-term debt, financing and capital lease obligations	5,603	4,690
Total current liabilities	11,689	11,963
Long-term debt, financing and capital lease obligations	31,354	29,268
Deferred tax liabilities	14,006	13,959
Note due to consolidated affiliate	0	0
Other liabilities	3,844	4,002
Due to affiliate	0	0
Total liabilities	60,893	59,192
Commitments and contingencies
Total stockholders' equity	19,502	19,783
Liabilities and Equity	80,395	78,975
Consolidation, Eliminations [Member]
Current Assets
Cash and Cash Equivalents	0	0			0	0
Short-term Investments	0
Accounts and notes receivable, net	(196)	(114)
Device and accessory inventory	0	0
Prepaid expenses and other current assets	0	0
Total current assets	(196)	(114)
Investments in Subsidiaries	(43,229)	(42,912)
Property, plant and equipment, net	0	0
Due from Affiliate, Noncurrent	(17,097)	(19,568)
Note receivable from consolidated affiliate	(10,653)	(10,622)
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	0	0
FCC licenses and other	0	0
Definite-lived intangible assets, net	0	0
Other assets	0	(1,019)
Total assets	(71,175)	(74,235)
Current Liabilities
Accounts Payable, Current	0	0
Accrued expenses and other current liabilities	(196)	(114)
Current portion of long-term debt, financing and capital lease obligations	0	0
Total current liabilities	(196)	(114)
Long-term debt, financing and capital lease obligations	0	(1,019)
Deferred tax liabilities	0	0
Note due to consolidated affiliate	(10,653)	(10,622)
Other liabilities	0	0
Due to affiliate	(17,097)	(19,568)
Total liabilities	(27,946)	(31,323)
Total stockholders' equity	(43,229)	(42,912)
Liabilities and Equity	(71,175)	(74,235)
Parent Company [Member]
Current Assets
Cash and Cash Equivalents	0	0			0	0
Short-term Investments	0
Accounts and notes receivable, net	196	87
Device and accessory inventory	0	0
Prepaid expenses and other current assets	0	0
Total current assets	196	87
Investments in Subsidiaries	19,502	19,783
Property, plant and equipment, net	0	0
Due from Affiliate, Noncurrent	42	50
Note receivable from consolidated affiliate	10,381	10,377
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	0	0
FCC licenses and other	0	0
Definite-lived intangible assets, net	0	0
Other assets	0	0
Total assets	30,121	30,297
Current Liabilities
Accounts Payable, Current	0	0
Accrued expenses and other current liabilities	238	137
Current portion of long-term debt, financing and capital lease obligations	0	0
Total current liabilities	238	137
Long-term debt, financing and capital lease obligations	10,381	10,377
Deferred tax liabilities	0	0
Note due to consolidated affiliate	0	0
Other liabilities	0	0
Due to affiliate	0	0
Total liabilities	10,619	10,514
Total stockholders' equity	19,502	19,783
Liabilities and Equity	30,121	30,297
Guarantor Subsidiaries [Member]
Current Assets
Cash and Cash Equivalents	3,338	2,154			1,521	3,492
Short-term Investments	1,269
Accounts and notes receivable, net	0	27
Device and accessory inventory	0	0
Prepaid expenses and other current assets	15	12
Total current assets	4,622	2,193
Investments in Subsidiaries	23,727	23,129
Property, plant and equipment, net	0	0
Due from Affiliate, Noncurrent	17,055	19,518
Note receivable from consolidated affiliate	272	245
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	0	0
FCC licenses and other	0	0
Definite-lived intangible assets, net	0	0
Other assets	197	1,127
Total assets	45,873	46,212
Current Liabilities
Accounts Payable, Current	0	0
Accrued expenses and other current liabilities	571	531
Current portion of long-term debt, financing and capital lease obligations	3,045	3,065
Total current liabilities	3,616	3,596
Long-term debt, financing and capital lease obligations	11,447	11,495
Deferred tax liabilities	0	0
Note due to consolidated affiliate	10,381	10,377
Other liabilities	927	961
Due to affiliate	0	0
Total liabilities	26,371	26,429
Total stockholders' equity	19,502	19,783
Liabilities and Equity	45,873	46,212
Non-Guarantor Subsidiaries [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Other Additional Capital	600
Current Assets
Cash and Cash Equivalents	442	487			$ 539	$ 518
Short-term Investments	35
Accounts and notes receivable, net	1,113	1,099
Device and accessory inventory	816	1,173
Prepaid expenses and other current assets	1,934	1,908
Total current assets	4,340	4,667
Investments in Subsidiaries	0	0
Property, plant and equipment, net	19,715	20,297
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	40,175	40,073
Definite-lived intangible assets, net	4,157	4,469
Other assets	614	620
Total assets	75,576	76,701
Current Liabilities
Accounts Payable, Current	1,841	2,899
Accrued expenses and other current liabilities	3,632	3,820
Current portion of long-term debt, financing and capital lease obligations	2,558	1,625
Total current liabilities	8,031	8,344
Long-term debt, financing and capital lease obligations	9,526	8,415
Deferred tax liabilities	14,006	13,959
Note due to consolidated affiliate	272	245
Other liabilities	2,917	3,041
Due to affiliate	17,097	19,568
Total liabilities	51,849	53,572
Total stockholders' equity	23,727	23,129
Liabilities and Equity	$ 75,576	$ 76,701