Preferred And Common Stock (Narrative) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended	12 Months Ended				12 Months Ended				1 Months Ended	12 Months Ended						1 Months Ended									12 Months Ended
	Jun. 30, 2009	Apr. 30, 2012	Apr. 30, 2011	Apr. 30, 2010	Apr. 30, 2012 Director Stock Plan [Member]	Apr. 30, 2012 Stock Options [Member]	Apr. 30, 2010 Stock Options [Member]	Apr. 30, 2011 Stock Options [Member]	Apr. 30, 2009 Stock Options [Member]	Jun. 30, 2011 Restricted Stock Units (RSUs) [Member]	Apr. 30, 2012 Restricted Stock Units (RSUs) [Member]	Apr. 30, 2011 Restricted Stock Units (RSUs) [Member]	Apr. 30, 2010 Restricted Stock Units (RSUs) [Member]	Apr. 30, 2009 Restricted Stock Units (RSUs) [Member]	Apr. 30, 2012 Plan And Prior Plan [Member]	Apr. 30, 2012 Non-Employee, Certain Officers, Key Employees [Member]	May 31, 2009 Non-Employee [Member]	Sep. 30, 2011 Non-Employee [Member] Restricted Stock Units (RSUs) [Member]	Mar. 31, 2011 Non-Employee [Member] Restricted Stock Units (RSUs) [Member]	Jun. 30, 2010 Non-Employee [Member] Restricted Stock Units (RSUs) [Member]	Jun. 30, 2011 Certain Officers And Key Employees [Member]	Jun. 30, 2009 Certain Officers And Key Employees [Member]	Jun. 30, 2011 Certain Employees [Member] Restricted Stock Units (RSUs) [Member]	Jun. 30, 2011 Chief Executive Officer [Member] Restricted Stock Units (RSUs) [Member]	Apr. 30, 2012 Series A Preferred Stock [Member]	Apr. 30, 2012 Minimum [Member]	Apr. 30, 2012 Maximum [Member]
Preferred And Common Stock [Line Items]
Preferred stock, shares authorized		1,000,000																							250,000
Common stock, shares authorized		120,000,000
Price of 1/1000th of Series A share		$ 95.00
Shares available for grant		4,428,604			200,000											5,260,000
Stock options outstanding						1,053,509	959,550	775,109	678,000		66,198	28,000				1,053,509
Stock granted						441,000	377,000			15,000	38,198	28,000					16,000	14,000	14,000	14,000	441,000	361,000	9,198
Stock options, expiration date																										2013	2021
Date vested	2012-06-23																	2012-05-01	2011-05-01		2012-06-23		2014-06-10	June 23, 2014
Aggregate intrinsic value of options outstanding		$ 25,029
Weighted average remaining contractual life of options outstanding (years)		7 years 2 months 12 days
Options vested		276,009
Weighted average exercise price of options vested		$ 22.82
Weighted average remaining contractual life of vested options (years)		5 years 9 months 18 days
Aggregate intrinsic value of options vested		9,255
Aggregate intrinsic value of options exercised		4,565
Total fair value of shares granted		6,461
Total compensation costs		3,792	2,066	2,031
Unrecognized compensation costs															$ 4,894