Corporate Debt (Interest Expense) (Details) (Convertible Senior Subordinated Notes [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Contractual interest coupon	$ 1,306	$ 1,082
Amortization of discount on liability component and debt issuance costs	1,824	2,165
Interest expense, total	3,130	3,247
October 2004 Notes [Member]
Contractual interest coupon	5	266
Amortization of discount on liability component and debt issuance costs	0	616
Interest expense, total	5	882
Coupon rate	2.9375%
Effective interest rate of liability component	9.65%
February 2005 Notes [Member]
Contractual interest coupon	248	213
Amortization of discount on liability component and debt issuance costs	6	374
Interest expense, total	254	587
Coupon rate	3.625%
Effective interest rate of liability component	10.03%
April 2009 Notes [Member]
Contractual interest coupon	603	603
Amortization of discount on liability component and debt issuance costs	1,398	1,175
Interest expense, total	2,001	1,778
Coupon rate	3.625%
Effective interest rate of liability component	17.26%
January 2012 Notes [Member]
Contractual interest coupon	450	0
Amortization of discount on liability component and debt issuance costs	420	0
Interest expense, total	$ 870	$ 0
Coupon rate	4.00%
Effective interest rate of liability component	9.56%