Disclosure Of Compensation Related Costs, Share Based Payments (Narrative) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	9 Months Ended		1 Months Ended		0 Months Ended		1 Months Ended			9 Months Ended
	Jan. 31, 2012 years	Jan. 31, 2011	Jun. 23, 2011 Stock Options [Member]	Jan. 31, 2012 2009 Stock Incentive Plan [Member]	Sep. 16, 2011 Restricted Stock [Member]	Jun. 10, 2011 Restricted Stock [Member]	Jun. 23, 2011 Restricted Stock [Member]	Jan. 31, 2012 Restricted Stock [Member]	Jan. 31, 2012 Plan And Prior Plans [Member]	Jan. 31, 2012 Maximum [Member]	Jan. 31, 2012 Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Each award of stock options issued, reduction in shares available amount	1
Each award of restricted stock or restricted unit issued, reduction in shares available amount	2
Shares available for grant				4,428,604
Restricted shares granted					14,000	9,198	15,000
Date vested			June 23, 2014		May 1, 2012	May 1, 2014	June 23, 2014
Stock granted	441,000		441,000
Share-based compensation, cost to grantee			$ 0		$ 0	$ 0	$ 0
Stock options, expiration date										2021	2012
Aggregate intrinsic value of options outstanding	21,212
Weighted average remaining contractual life of options outstanding (years)	7.2
Options vested	338,909
Weighted average exercise price of options vested	$ 22.48
Weighted average remaining contractual life of vested options (years)	4.2
Aggregate intrinsic value of options vested	9,644
Aggregate intrinsic value of options exercised	2,472
Total fair value of shares granted	6,461
Total compensation costs	2,657	1,305
Unrecognized compensation costs								$ 1,082	$ 5,676