Consolidating Financial Information - Convertible Senior Subordinated Notes (Narrative) (Details) (Convertible Senior Subordinated Notes [Member])	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
October 2004 Notes [Member]
Coupon rate	2.9375%	2.9375%	2.9375%
February 2005 Notes [Member]
Coupon rate	3.625%		3.625%
April 2009 Notes [Member]
Coupon rate	3.625%
January 2012 Notes [Member]
Coupon rate	4.00%	4.00%