Capital Stock (Common Shares Reserved for Future Issuance) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2012	Mar. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance	21,037	22,535
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance	3,157	3,310
Average exercise price on stock options	10.20	9.75
Restricted Share Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance	1,867	1,801
Purchase Options and Restricted Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance	1,984	3,683
October 2004 Notes [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance	30	4,028
Coupon rate	2.9375%
Conversion price per share	11.50
February 2005 Notes [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance	1,643	1,643
Coupon rate	3.625%
Conversion price per share	14.28
April 2009 Notes [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance	8,070	8,070
Coupon rate	3.625%
Conversion price per share	8.25
January 2012 Notes [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance	4,286	0
Coupon rate	4.00%
Conversion price per share	10.50