Accumulated Other Comprehensive Income (Loss) Components of Net of Tax (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
Balance as of March 31, 2012			$ (45,436)
Foreign currency translation	(1,068)	1,578	462	(4,179)
Unrealized loss on investments	11,794	9,178	19,991	5,169
Change in fair value of cash flow hedges			2,791
Other comprehensive income (loss), net of tax, increase (decrease)			23,244
Balance as of December 31, 2012	(22,192)		(22,192)
Foreign Currency Translation
Balance as of March 31, 2012			(28,882)
Foreign currency translation			462
Other comprehensive income (loss), net of tax, increase (decrease)			462
Balance as of December 31, 2012	(28,420)		(28,420)
Unrealized Gain (Loss) on Investments
Balance as of March 31, 2012			20,866
Unrealized loss on investments			19,991
Other comprehensive income (loss), net of tax, increase (decrease)			19,991
Balance as of December 31, 2012	40,857		40,857
Fair Market Value of Cash Flow Hedges
Balance as of March 31, 2012			(38,129)
Change in fair value of cash flow hedges			2,791
Other comprehensive income (loss), net of tax, increase (decrease)			2,791
Balance as of December 31, 2012	(35,338)		(35,338)
Postretirement Benefit Obligation Gain (Loss)
Balance as of March 31, 2012			709
Other comprehensive income (loss), net of tax, increase (decrease)			0
Balance as of December 31, 2012	$ 709		$ 709