Guarantor Financial Information (CONDENSED CONSOLIDATING BALANCE SHEET) (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Apr. 01, 2019	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2017
Condensed Balance Sheet Statements, Captions [Line Items]
Operating Lease, Liability, Current	$ 1,680		$ 1,813
Depreciation, network and other	1,120	$ 1,023
Current Assets
Cash and Cash Equivalents	4,869			$ 6,982	$ 6,659	$ 4,425
Short-term Investments	0			67
Accounts and notes receivable, net	3,558			3,554
Due from Affiliate, Current	0			0
Device and accessory inventory	726			999
Prepaid expenses and other current assets	1,436		1,178	1,289
Total current assets	10,589			12,891
Investments in Subsidiaries	0			0
Property, plant and equipment, net	20,556		21,197	21,201
Costs to acquire a customer contract	1,631			1,559
Operating Lease, Right-of-Use Asset	7,054		7,358
Due from Consolidated Affiliate	0			0
Due from Affiliate, Noncurrent	0			0
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	4,598			4,598
FCC licenses and other	41,474			41,465
Property, plant and equipment	1,525		1,650	1,769
Other assets	1,119		1,117	1,118
Total assets	88,546			84,601
Current Liabilities
Accounts Payable, Current	3,672			3,961
Accrued expenses and other current liabilities	3,048		3,419	3,597
Current portion of long-term debt, financing and capital lease obligations	2,889		4,514	4,557
Due to Affiliate, Current	0			0
Total current liabilities	11,289			12,115
Long-term debt, financing and capital lease obligations	35,073		35,299	35,366
Operating Lease, Liability, Noncurrent	5,913		6,263
Note due to consolidated affiliate	0			0
Deferred tax liabilities	7,563		7,602	7,556
Other liabilities	2,540		$ 2,564	3,437
Due to affiliate	0			0
Total liabilities	62,378			58,474
Commitments and contingencies
Total stockholders' equity	26,116			26,072
Stockholders' Equity Attributable to Noncontrolling Interest	52			55
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	26,168	27,945		26,127	26,419
Liabilities and Equity	88,546			84,601
Depreciation, equipment rentals	1,029	1,136
Consolidation, Eliminations [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Operating Lease, Liability, Current	0
Depreciation, network and other	0	0
Current Assets
Cash and Cash Equivalents	0			0	0	0
Short-term Investments				0
Accounts and notes receivable, net	(706)			(329)
Due from Affiliate, Current	(424)			(424)
Device and accessory inventory	0			0
Prepaid expenses and other current assets	0			0
Total current assets	(1,130)			(753)
Investments in Subsidiaries	(43,228)			(43,148)
Property, plant and equipment, net	0			0
Costs to acquire a customer contract	0			0
Operating Lease, Right-of-Use Asset	0
Due from Consolidated Affiliate	(5,190)			(2,706)
Due from Affiliate, Noncurrent	(35,032)			(35,450)
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	0			0
FCC licenses and other	0			0
Property, plant and equipment	0			0
Other assets	0			0
Total assets	(84,580)			(82,057)
Current Liabilities
Accounts Payable, Current	0			0
Accrued expenses and other current liabilities	(706)			(329)
Current portion of long-term debt, financing and capital lease obligations	0			0
Due to Affiliate, Current	(424)			(424)
Total current liabilities	(1,130)			(753)
Long-term debt, financing and capital lease obligations	0			0
Operating Lease, Liability, Noncurrent	0
Note due to consolidated affiliate	(35,032)			(35,450)
Deferred tax liabilities	0			0
Other liabilities	0			0
Due to affiliate	(5,190)			(2,706)
Total liabilities	(41,352)			(38,909)
Commitments and contingencies
Total stockholders' equity	(43,228)			(43,148)
Stockholders' Equity Attributable to Noncontrolling Interest	0			0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	(43,228)			(43,148)
Liabilities and Equity	(84,580)			(82,057)
Depreciation, equipment rentals	0	0
Parent Company [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Operating Lease, Liability, Current	0
Depreciation, network and other	0	0
Current Assets
Cash and Cash Equivalents	0			0	0	0
Short-term Investments				0
Accounts and notes receivable, net	233			96
Due from Affiliate, Current	0			0
Device and accessory inventory	0			0
Prepaid expenses and other current assets	0			0
Total current assets	233			96
Investments in Subsidiaries	25,832			25,785
Property, plant and equipment, net	0			0
Costs to acquire a customer contract	0			0
Operating Lease, Right-of-Use Asset	0
Due from Consolidated Affiliate	290			288
Due from Affiliate, Noncurrent	11,889			11,883
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	0			0
FCC licenses and other	0			0
Property, plant and equipment	0			0
Other assets	0			0
Total assets	38,244			38,052
Current Liabilities
Accounts Payable, Current	0			0
Accrued expenses and other current liabilities	239			97
Current portion of long-term debt, financing and capital lease obligations	0			0
Due to Affiliate, Current	0			0
Total current liabilities	239			97
Long-term debt, financing and capital lease obligations	11,889			11,883
Operating Lease, Liability, Noncurrent	0
Note due to consolidated affiliate	0			0
Deferred tax liabilities	0			0
Other liabilities	0			0
Due to affiliate	0			0
Total liabilities	12,128			11,980
Commitments and contingencies
Total stockholders' equity	26,116			26,072
Stockholders' Equity Attributable to Noncontrolling Interest	0			0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	26,116			26,072
Liabilities and Equity	38,244			38,052
Depreciation, equipment rentals	0	0
Guarantor Subsidiaries [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Operating Lease, Liability, Current	0
Depreciation, network and other	0	0
Current Assets
Cash and Cash Equivalents	4,469			6,605	6,222	3,962
Short-term Investments				67
Accounts and notes receivable, net	473			233
Due from Affiliate, Current	424			424
Device and accessory inventory	0			0
Prepaid expenses and other current assets	17			9
Total current assets	5,383			7,338
Investments in Subsidiaries	17,396			17,363
Property, plant and equipment, net	0			0
Costs to acquire a customer contract	0			0
Operating Lease, Right-of-Use Asset	0
Due from Consolidated Affiliate	4,900			2,418
Due from Affiliate, Noncurrent	23,143			23,567
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	0			0
FCC licenses and other	0			0
Property, plant and equipment	0			0
Other assets	40			52
Total assets	50,862			50,738
Current Liabilities
Accounts Payable, Current	0			0
Accrued expenses and other current liabilities	348			230
Current portion of long-term debt, financing and capital lease obligations	1,369			1,373
Due to Affiliate, Current	0			0
Total current liabilities	1,717			1,603
Long-term debt, financing and capital lease obligations	10,636			10,660
Operating Lease, Liability, Noncurrent	0
Note due to consolidated affiliate	11,889			11,883
Deferred tax liabilities	0			0
Other liabilities	788			807
Due to affiliate	0			0
Total liabilities	25,030			24,953
Commitments and contingencies
Total stockholders' equity	25,832			25,785
Stockholders' Equity Attributable to Noncontrolling Interest	0			0
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	25,832			25,785
Liabilities and Equity	50,862			50,738
Depreciation, equipment rentals	0	0
Non-Guarantor Subsidiaries [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Operating Lease, Liability, Current	1,680
Depreciation, network and other	1,120	1,023
Other Additional Capital	37					1,500
Current Assets
Cash and Cash Equivalents	400			377	$ 437	$ 463
Short-term Investments				0
Accounts and notes receivable, net	3,558			3,554
Due from Affiliate, Current	0			0
Device and accessory inventory	726			999
Prepaid expenses and other current assets	1,419			1,280
Total current assets	6,103			6,210
Investments in Subsidiaries	0			0
Property, plant and equipment, net	20,556			21,201
Costs to acquire a customer contract	1,631			1,559
Operating Lease, Right-of-Use Asset	7,054
Due from Consolidated Affiliate	0			0
Due from Affiliate, Noncurrent	0			0
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	4,598			4,598
FCC licenses and other	41,474			41,465
Property, plant and equipment	1,525			1,769
Other assets	1,079			1,066
Total assets	84,020			77,868
Current Liabilities
Accounts Payable, Current	3,672			3,961
Accrued expenses and other current liabilities	3,167			3,599
Current portion of long-term debt, financing and capital lease obligations	1,520			3,184
Due to Affiliate, Current	424			424
Total current liabilities	10,463			11,168
Long-term debt, financing and capital lease obligations	12,548			12,823
Operating Lease, Liability, Noncurrent	5,913
Note due to consolidated affiliate	23,143			23,567
Deferred tax liabilities	7,563			7,556
Other liabilities	1,752			2,630
Due to affiliate	5,190			2,706
Total liabilities	66,572			60,450
Commitments and contingencies
Total stockholders' equity	17,396			17,363
Stockholders' Equity Attributable to Noncontrolling Interest	52			55
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest	17,448			17,418
Liabilities and Equity	84,020			$ 77,868
Depreciation, equipment rentals	$ 1,029	$ 1,136