Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net loss	$ 3,391	$ 8,062	$ (5,136)	$ (1,675)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation			157,939	135,144
Amortization of intangible assets			31,675	31,206
Stock-based compensation expense	22,400	21,100	43,328	42,328
Loss on disposition of fixed assets			17,678	23,566
Other non-cash adjustments			(2,354)	(4,023)
Increase (decrease) in cash resulting from changes in operating assets and liabilities:
Accounts receivable			73,856	893
Inventories			(38,034)	(34,091)
Other assets			19,513	(6,403)
Accounts payable			(14,481)	5,582
Accrued liabilities			52,510	(2,292)
Other liabilities			(2,972)	(6,943)
Net cash provided by operating activities			333,522	183,292
Cash flows from investing activities:
Purchase of property, equipment and satellites			(426,298)	(329,558)
Cash paid for patents, licenses and other assets			(33,586)	(35,445)
Proceeds from insurance claims on ViaSat-2 satellite				2,277	$ 188,000	$ 188,000
Net cash used in investing activities			(459,884)	(362,726)
Cash flows from financing activities:
Proceeds from debt borrowings			400,000
Payments of debt borrowings			(402,940)	(14,821)
Payment of debt issuance costs			(4,882)	(2,479)
Proceeds from issuance of common stock under equity plans			9,206	27,016
Purchase of common stock in treasury (immediately retired) related to tax withholdings for stock-based compensation			(747)	(3,128)
Proceeds from common stock issued in private placement, net of issuance costs			174,749
Other financing activities			(3,454)	(1,368)
Net cash provided by financing activities			171,932	5,220
Effect of exchange rate changes on cash			554	(442)
Net increase (decrease) in cash and cash equivalents			46,124	(174,656)
Cash and cash equivalents at beginning of period			304,309	261,701	261,701
Cash and cash equivalents at end of period	$ 350,433	$ 87,045	$ 350,433	$ 87,045	$ 304,309	$ 261,701