Intangible Assets (Tables)

12 Months Ended

Mar. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Indefinite-Lived Intangible Assets

The following provides the activity of indefinite-lived intangible assets within the consolidated balance sheets:

	March 31, 2016		Net Additions			March 31, 2017
	(in millions)
FCC licenses	$	36,038	$	512	(1)	$	36,550
Trademarks	4,035		—			4,035
Goodwill (2)	6,575		4			6,579
	$	46,648	$	516		$	47,164

	March 31, 2015		Net Additions		March 31, 2016
	(in millions)
FCC licenses	$	35,952	$	86	$	36,038
Trademarks	4,035		—		4,035
Goodwill (2)	6,575		—		6,575
	$	46,562	$	86	$	46,648

Intangible Assets Subject to Amortization

		March 31, 2017							March 31, 2016
	Useful Lives	Gross Carrying Value		Accumulated Amortization			Net Carrying Value		Gross Carrying Value		Accumulated Amortization			Net Carrying Value
		(in millions)
Customer relationships	4 to 8 years	$	6,923	$	(5,053	)	$	1,870	$	6,923	$	(4,045	)	$	2,878
Other intangible assets:
Favorable spectrum leases	23 years	869		(138		)	731		881		(110		)	771
Favorable tower leases	7 years	589		(386		)	203		589		(302		)	287
Trademarks	34 years	520		(58		)	462		520		(43		)	477
Other	10 years	91		(37		)	54		83		(27		)	56
Total other intangible assets		2,069		(619		)	1,450		2,073		(482		)	1,591
Total definite-lived intangible assets		$	8,992	$	(5,672	)	$	3,320	$	8,996	$	(4,527	)	$	4,469

Intangible Assets Subject to Amortization, Future Amortization Expense

	Fiscal Year 2017		Fiscal Year 2018		Fiscal Year 2019		Fiscal Year 2020		Fiscal Year 2021
	(in millions)
Estimated amortization expense	$	883	$	667	$	462	$	258	$	104