Reconciliation of Weighted Average Shares Outstanding (Details)	3 Months Ended
	Jul. 31, 2012	Jul. 31, 2011
Reconciliation of Weighted Average Shares Outstanding [Abstract]
Weighted average shares outstanding (in shares)	59,675,000	60,857,000
Less: Unearned restricted shares (in shares)	(188,000)	(187,000)
Shares used for basic earnings per share (in shares)	59,487,000	60,670,000
Dilutive effect of stock options and other stock awards (in shares)	946,000	1,154,000
Shares used for diluted earnings per share (in shares)	60,433,000	61,824,000
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded for diluted EPS calculation (in shares)	1,428,410	410,568
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive shares excluded for diluted EPS calculation (in shares)	19,500	43,150