Corporate Debt (Interest Expense) (Details) (Convertible Senior Subordinated Notes [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
Contractual interest coupon	$ 1,191	$ 1,049	$ 3,581	$ 3,489
Amortization of discount on liability component and debt issuance costs	2,195	1,999	6,432	5,722
Interest expense, total	3,386	3,048	10,013	9,211
October 2004 Notes [Member]
Contractual interest coupon	2	5	7	10
Interest expense, total	2	5	7	10
Coupon rate	2.9375%		2.9375%
Effective interest rate of liability component	9.65%		9.65%
February 2005 Notes [Member]
Contractual interest coupon	0	0	0	328
Amortization of discount on liability component and debt issuance costs	0	0	0	6
Interest expense, total	0	0	0	334
Coupon rate	3.625%	3.625%	3.625%	3.625%
Effective interest rate of liability component	10.03%		10.03%
April 2009 Notes [Member]
Contractual interest coupon	584	594	1,748	1,801
Amortization of discount on liability component and debt issuance costs	1,746	1,559	5,073	4,427
Interest expense, total	2,330	2,153	6,821	6,228
Coupon rate	3.625%	3.625%	3.625%	3.625%
Effective interest rate of liability component	17.26%		17.26%
January 2012 Notes [Member]
Contractual interest coupon	418	450	1,295	1,350
Amortization of discount on liability component and debt issuance costs	449	440	1,359	1,289
Interest expense, total	867	890	2,654	2,639
Coupon rate	4.00%		4.00%
Effective interest rate of liability component	9.56%		9.56%
April 2013 Notes [Member]
Contractual interest coupon	187	0	531	0
Interest expense, total	$ 187	$ 0	$ 531	$ 0
Coupon rate	1.25%		1.25%