Capital Stock (Share-Based Compensation Expense) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Share-Based Compensation Expense [Line Items]
Total share-based compensation expense	$ 22,388		$ 6,899		$ 40,135		$ 16,648
Tax impact	(8,284)	[1]	0	[1]	(14,850)	[1]	0	[1]
Reduction in net income	14,104		6,899		25,285		16,648
Stock Options [Member]
Share-Based Compensation Expense [Line Items]
Total share-based compensation expense	5,971		356		9,738		655
Restricted Share Units and Other Share-based Compensation [Member]
Share-Based Compensation Expense [Line Items]
Total share-based compensation expense	8,032		4,404		15,435		11,628
Stock Appreciation Rights (SARs) [Member]
Share-Based Compensation Expense [Line Items]
Total share-based compensation expense	$ 8,385		$ 2,139		$ 14,962		$ 4,365

[1] Represents the income tax benefit recognized in the statements of operations for share-based compensation arrangements.