Accumulated Other Comprehensive Income Loss (Details) - USD ($) $ in Thousands	12 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Balance as of March 31, 2019	$ (66,698)
Foreign currency translation	9,377	$ (1,759)	$ 14,652
Unrealized net loss on investments	97,943		20,104
Change in fair value of cash flow hedges			3,082
Amounts reclassified into earnings on hedging activities	(401)	789	3,893
Change in postretirement benfit obligations	333	(1,025)	35
Other comprehensive income (loss)	101,350	(62,075)	37,873
Balance as of March 31, 2020	34,652	(66,698)
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Balance as of March 31, 2019	(56,612)
Foreign currency translation	9,377
Unrealized net loss on investments	0
Change in fair value of cash flow hedges	0
Amounts reclassified into earnings on hedging activities	0
Change in postretirement benfit obligations	0
Other comprehensive income (loss)	9,377
Balance as of March 31, 2020	(47,235)	(56,612)
Unrealized Gain (Loss) on Investments
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Balance as of March 31, 2019	(7,259)
Foreign currency translation	0
Unrealized net loss on investments	97,943
Change in fair value of cash flow hedges	0
Amounts reclassified into earnings on hedging activities	0
Change in postretirement benfit obligations	0
Other comprehensive income (loss)	97,943
Balance as of March 31, 2020	90,684	(7,259)
Fair Market Value of Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Balance as of March 31, 2019	107
Foreign currency translation	0
Unrealized net loss on investments	0
Change in fair value of cash flow hedges	(6,301)
Amounts reclassified into earnings on hedging activities	(2)
Change in postretirement benfit obligations	0
Other comprehensive income (loss)	(6,303)
Balance as of March 31, 2020	(6,196)	107
Postretirement Benefit Obligation Gain (Loss)
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Balance as of March 31, 2019	(2,934)
Foreign currency translation	0	0	0
Unrealized net loss on investments	0	0	0
Change in fair value of cash flow hedges	0	0	0
Amounts reclassified into earnings on hedging activities	0
Change in postretirement benfit obligations		0	0
Other comprehensive income (loss)	333
Balance as of March 31, 2020	(2,601)	(2,934)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Balance as of March 31, 2019	(66,698)
Foreign currency translation	9,377	(1,759)	14,652
Unrealized net loss on investments	97,943	(50,044)	20,104
Change in fair value of cash flow hedges		477	3,082
Amounts reclassified into earnings on hedging activities	(2)
Change in postretirement benfit obligations	333	(1,025)	$ 35
Other comprehensive income (loss)	101,350
Balance as of March 31, 2020	$ 34,652	$ (66,698)

A roll forward schedule of the summary of accumulated other comprehensive income (loss) components, net of tax.

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Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

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The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

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Amount after tax and reclassification adjustments, of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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Amount, after tax, of increase (decrease) to other comprehensive income from settlement and curtailment gain (loss) of defined benefit plan.

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Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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