Accumulated Other Comprehensive Income (Loss) Components of Net of Tax (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Balance as of March 31, 2013	$ (22,680)
Foreign currency translation	(9,134)	(1,271)	(2,854)
Unrealized net loss on investments	(33,654)	18,779	10,005
Fair market value of cash flow hedges, net of tax	11,977	5,831	(5,691)
Change in postretirement benfit obligations	(432)	(583)	(429)
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	16,691	19,178	23,559
Balance as of March 31, 2014	(53,923)	(22,680)
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) Components, Net of Tax [Roll Forward]
Foreign currency translation	(9,134)	(1,271)	(2,854)
Unrealized net loss on investments	(33,654)	18,779	10,005
Fair market value of cash flow hedges, net of tax	11,977	5,831	(5,691)
Change in postretirement benfit obligations	$ (432)	$ (583)	$ (429)