Goodwill and Acquired Intangible Assets - Allocation of Other Acquired Intangible Assets and Related Accumulated Amortization (Detail) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Other acquired intangible assets, gross	$ 219,137	$ 215,091
Other acquired intangible assets, accumulated amortization	(187,275)	(173,414)
Other acquired intangible assets, net	$ 31,862	41,677
Technology [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life	6 years
Other acquired intangible assets, gross	$ 90,652	87,592
Other acquired intangible assets, accumulated amortization	(69,387)	(62,749)
Other acquired intangible assets, net	$ 21,265	24,843
Contracts and Customer Relationships [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life	7 years
Other acquired intangible assets, gross	$ 103,808	103,034
Other acquired intangible assets, accumulated amortization	(94,584)	(89,083)
Other acquired intangible assets, net	$ 9,224	13,951
Satellite Co-Location Rights [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life	9 years
Other acquired intangible assets, gross	$ 8,600	8,600
Other acquired intangible assets, accumulated amortization	(7,668)	(6,743)
Other acquired intangible assets, net	$ 932	1,857
Trade Name [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life	3 years
Other acquired intangible assets, gross	$ 5,940	5,940
Other acquired intangible assets, accumulated amortization	$ (5,940)	(5,940)
Other [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Weighted Average Useful Life	6 years
Other acquired intangible assets, gross	$ 10,137	9,925
Other acquired intangible assets, accumulated amortization	(9,696)	(8,899)
Other acquired intangible assets, net	$ 441	$ 1,026