Capital Stock (Details) (USD $)	1 Months Ended			12 Months Ended				12 Months Ended				1 Months Ended	12 Months Ended			1 Months Ended	12 Months Ended			1 Months Ended				1 Months Ended		1 Months Ended	12 Months Ended		1 Months Ended		12 Months Ended
	Jul. 31, 2012	May 31, 2011	May 31, 2010	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2012 2006 Plan and 2004 Director Plan	Jun. 30, 2012 2006 Plan Stock options	Jun. 30, 2011 2006 Plan Stock options	Jun. 30, 2010 2006 Plan Stock options	Nov. 30, 2001 2001 Director Plan	Nov. 30, 2011 2001 Director Plan Deferred share units	Jun. 30, 2012 2001 Director Plan Deferred share units	Jun. 30, 2011 2001 Director Plan Deferred share units	Jun. 30, 2010 2001 Director Plan Deferred share units	Jun. 30, 2004 2004 Director Plan Deferred share units	Jun. 30, 2012 2004 Director Plan Deferred share units	Jun. 30, 2011 2004 Director Plan Deferred share units	Jun. 30, 2010 2004 Director Plan Deferred share units	Sep. 30, 2006 2004 Amended Director Plan Deferred share units	Nov. 30, 2009 Compensation Policy for Non-Employee Directors Initial equity grant upon election to the Board	Nov. 11, 2009 Compensation Policy for Non-Employee Directors Initial equity grant upon election to the Board	Nov. 11, 2009 Compensation Policy for Non-Employee Directors Equity grant on first anniversary of initial election to the board	Nov. 30, 2009 Compensation Policy for Non-Employee Directors Annual equity grant	Nov. 11, 2009 Compensation Policy for Non-Employee Directors Annual equity grant	Sep. 30, 2010 Compensation Policy for Non-Employee Directors Stock options	Jun. 30, 2012 Compensation Policy for Non-Employee Directors Stock options	Jun. 30, 2011 Compensation Policy for Non-Employee Directors Stock options	Nov. 30, 2011 Compensation Policy for Non-Employee Directors Deferred share units item	Nov. 30, 2009 Compensation Policy for Non-Employee Directors Deferred share units	Jun. 30, 2012 Compensation Policy for Non-Employee Directors Deferred share units	Jun. 30, 2011 Compensation Policy for Non-Employee Directors Deferred share units	Jun. 30, 2010 Compensation Policy for Non-Employee Directors Deferred share units
Sale of Common Stock
Issuance of common stock through a public offering (in shares)	6,250,000	7,800,000	10,350,000
Price at which common stock is issued through a public offering (in dollars per share)	$ 16.00	$ 12.00	$ 8.00
Gross proceeds from issuance	$ 100,000,000	$ 93,600,000	$ 82,800,000		$ 87,980,000	$ 77,521,000
Stock-based Compensation
Aggregate number of common shares reserved for future issuance							9,780,000
Options exercised (in shares)								1,432,000
Exercise price (in dollars per share)								$ 2.91
Exercise price (in dollars per share)								$ 11.18
Proceeds from stock options exercised				6,988,000	2,719,000	3,462,000		6,988,000	2,719,000	3,462,000
Exercisable (in shares)								3,416,000	3,834,000	4,011,000
Weighted-Average Exercise Price (in dollars per share)								$ 6.34	$ 5.25	$ 6.88
Common stock reserved for grant (in shares)											50,000
Compensation expense								9,900,000	5,500,000	4,200,000			29,000	44,000	10,000																314,000	326,000	460,000
Stock units outstanding (in shares)													6,000	15,000	15,000
Payment to retiring director to settle outstanding stock units												115,000
Monthly vesting rights (as a percent)																8.30%
Vesting period																				3 years	3 years			1 year		1 year
Aggregate market value of award																						65,000	30,000		30,000
Maximum vesting period from the date units were credited to the non-employee director for the award to be vested on September 16, 2009																1 year
Number of shares of common stock issued under 2009 Compensation Policy for each vested deferred stock unit held on the date a director ceases to be a member																														1
Number of retiring directors to whom common stock is issued																													2
Grant date fair value																										$ 30,000
Stock options granted to directors (in shares)								1,657,000																			33,187	49,688
Share units issued																	264,000	225,000	183,000												33,000	39,000	42,000
Common stock issued to settle retiring directors' share units																													46,298