Earnings per Share (Tables)

3 Months Ended

Jul. 31, 2011

Earnings Per Share (Tables) [Abstract]

Computation of Earnings Per Common Share

	Three Months Ended July 31,
	2011		2010
Computation of net income per share:
Net income	$	111,523	$	102,881
Net income allocated to participating securities		1,127		987
Net income allocated to common shareholders	$	110,396	$	101,894
Weighted-average common shares outstanding		113,122,789		118,156,815
Net income per common share	$	0.98	$	0.86

Computation of Earnings Per Common Share - assuming dilution

	Three Months Ended July 31,
	2011		2010
Computation of net income per share — assuming dilution:
Net income	$	111,523	$	102,881
Net income allocated to participating securities		1,127		986
Net income allocated to common shareholders	$	110,396	$	101,895
Weighted-average common shares outstanding		113,122,789		118,156,815
Dilutive effect of stock options		57,637		139,564
Weighted-average common shares outstanding — assuming dilution		113,180,426		118,296,379
Net income per common share — assuming dilution	$	0.98	$	0.86

Weighted-average common shares, basic and diluted

	Three Months Ended July 31,
	2011		2010
Weighted-average common shares outstanding		113,122,789		118,156,815
Weighted-average participating shares outstanding		1,154,758		1,144,111
Total weighted-average shares outstanding		114,277,547		119,300,926
Dilutive effect of stock options		57,637		139,564
Total weighted-average shares outstanding — assuming dilution		114,335,184		119,440,490