Accumulated Other Comprehensive Income (Loss) Components of Net of Tax (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Foreign Currency Translation	Sep. 30, 2012 Unrealized Gain (Loss) on Investments	Sep. 30, 2012 Fair Market Value of Cash Flow Hedges	Sep. 30, 2012 Postretirement Benefit Obligation Gain (Loss)	Mar. 31, 2012 Postretirement Benefit Obligation Gain (Loss)
Balance as of March 31, 2012			$ (45,436)		$ (28,882)	$ 20,866	$ (38,129)	$ 709	$ 709
Foreign currency translation	3,459	(6,749)	1,530	(5,757)	1,530
Unrealized loss on investments	6,904	(632)	8,197	(4,009)		8,197
Change in fair value of cash flow hedges			157				157
Other comprehensive income (loss), net of tax, increase (decrease)			9,884		1,530	8,197	157
Balance as of September 30, 2012	$ (35,552)		$ (35,552)		$ (27,352)	$ 29,063	$ (37,972)	$ 709	$ 709