Comprehensive Income (Loss) (Accumulated other comprehensive income (loss) components of net of tax) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax
Balance as of March 31, 2015			$ (34,365)
Foreign currency translation	$ (6,727)	$ (3,213)	(17,292)	$ (6,752)
Unrealized net gain on investments	666	(1,923)	(12,965)	28,719
Change in fair value of cash flow hedges	2,699	$ 980	5,554	4,599
Amount reclassified from AOCI			9,736	$ 10,919
Balance as of December 31, 2015	(59,068)		(59,068)
Foreign Currency Translation [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax
Balance as of March 31, 2015			(59,170)
Foreign currency translation			$ (17,292)
Unrealized net gain on investments
Change in fair value of cash flow hedges
Amount reclassified from AOCI
Other comprehensive income (loss)			$ (17,292)
Balance as of December 31, 2015	(76,462)		(76,462)
Unrealized Net Gain on Investments [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax
Balance as of March 31, 2015			$ 41,181
Foreign currency translation
Unrealized net gain on investments			$ (12,965)
Change in fair value of cash flow hedges
Amount reclassified from AOCI
Other comprehensive income (loss)			$ (12,965)
Balance as of December 31, 2015	28,216		28,216
Fair Market Value of Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax
Balance as of March 31, 2015			$ (15,235)
Foreign currency translation
Unrealized net gain on investments
Change in fair value of cash flow hedges			$ 15,290
Amount reclassified from AOCI			(9,736)
Other comprehensive income (loss)			5,554
Balance as of December 31, 2015	(9,681)		(9,681)
Postretirement Benefit Obligation Gain [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax
Balance as of March 31, 2015			$ (1,141)
Foreign currency translation
Unrealized net gain on investments
Change in fair value of cash flow hedges
Amount reclassified from AOCI
Other comprehensive income (loss)
Balance as of December 31, 2015	(1,141)		$ (1,141)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax
Balance as of March 31, 2015			(34,365)
Foreign currency translation			(17,292)
Unrealized net gain on investments			(12,965)
Change in fair value of cash flow hedges			15,290
Amount reclassified from AOCI			(9,736)
Other comprehensive income (loss)			(24,703)
Balance as of December 31, 2015	$ (59,068)		$ (59,068)