Accumulated Other Comprehensive Income (Loss) Components of Net of Tax (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012 Foreign Currency Translation	Jun. 30, 2012 Unrealized Gain (Loss) on Investments	Jun. 30, 2012 Fair Market Value of Cash Flow Hedges	Jun. 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	(1,929)	992	(1,929)
Unrealized loss on investments	1,293	(3,377)		1,293
Change in fair value of cash flow hedges	(319)				(319)
Other comprehensive income (loss), net of tax, increase (decrease)	(955)		(1,929)	1,293	(319)
Balance as of June 30, 2012	$ (46,391)		$ (30,811)	$ 22,159	$ (38,448)	$ 709	$ 709