Preferred And Common Stock (Narrative) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended				12 Months Ended				12 Months Ended					1 Months Ended				12 Months Ended	1 Months Ended	0 Months Ended	1 Months Ended	12 Months Ended	1 Months Ended		12 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011	Apr. 30, 2013 Director Stock Plan [Member]	Apr. 30, 2013 Stock Options [Member]	Apr. 30, 2012 Stock Options [Member]	Apr. 30, 2011 Stock Options [Member]	Apr. 30, 2010 Stock Options [Member]	Apr. 30, 2013 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, 2013 Non-Employee, Certain Officers, Key Employees [Member]	Sep. 14, 2012 Non-Employee [Member] Restricted Stock Units (RSUs) [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]	Apr. 30, 2013 Non-Employee [Member] Restricted Stock Units (RSUs) [Member]	Jun. 30, 2011 Certain Officers And Key Employees [Member]	Jun. 08, 2012 Certain Employees [Member] Restricted Stock Units (RSUs) [Member]	Jun. 30, 2011 Certain Employees [Member] Restricted Stock Units (RSUs) [Member]	Apr. 30, 2013 Certain Employees [Member] Restricted Stock Units (RSUs) [Member]	Jun. 30, 2011 Chief Executive Officer [Member] Restricted Stock Units (RSUs) [Member]	Apr. 30, 2013 Series A Preferred Stock [Member]	Apr. 30, 2013 Minimum [Member]	Apr. 30, 2013 Minimum [Member] Stock Options [Member]	Apr. 30, 2013 Maximum [Member]	Apr. 30, 2013 Maximum [Member] Stock Options [Member]
Preferred And Common Stock [Line Items]
Preferred stock, shares authorized	1,000,000																							250,000
Common stock, shares authorized	120,000,000
Shares available for grant	4,334,608			200,000
Stock options outstanding	854,809				854,809	1,053,509	775,109	959,550	113,196	66,198	28,000		854,809
Stock granted						441,000			46,998	38,198	28,000				14,000	14,000	14,000	14,000	441,000	32,998	9,198		15,000
Stock options, expiration date																									2013		2021
Date vested															May 01, 2012	May 01, 2011		May 01, 2013	Jun. 23, 2014		May 01, 2014	Jun. 08, 2015	Jun. 23, 2014
Aggregate intrinsic value of options outstanding	$ 19,903
Weighted average remaining contractual life of options outstanding (years)	6 years 7 months 6 days
Options vested	424,809
Option vesting period																										3 years		5 years
Weighted average exercise price of options vested	$ 24.74
Weighted average remaining contractual life of vested options (years)	5 years 1 month 6 days
Aggregate intrinsic value of options vested	14,089
Aggregate intrinsic value of options exercised	6,828
Total fair value of shares vested	2,928
Vested units									42,000
Nonvested Units									71,196
Total compensation costs	4,270	3,792	2,066
Unrecognized compensation costs					$ 4,141
Grant date fair value of options					$ 14.65									$ 58.93	$ 47.59	$ 36.68	$ 35.94			$ 59.48	$ 40.49		$ 44.39
Exercise price, lower range					$ 14.08
Exercise price, upper range					$ 44.39