Earnings per Share (Tables)

3 Months Ended

Jul. 31, 2012

Earnings Per Share [Abstract]

Computation of Earnings Per Common Share

	Three Months Ended July 31,
	2012		2011
Computation of net income per common share:
Net income	$	110,863	$	111,523
Net income allocated to participating securities		954		1,127
Net income allocated to common stockholders	$	109,909	$	110,396
Weighted-average common shares outstanding		109,418,592		113,122,789
Net income per common share	$	1.00	$	0.98

Computation of Earnings Per Common Share - assuming dilution

Computation of net income per common share - assuming dilution:
Net income	$	110,863	$	111,523
Net income allocated to participating securities		954		1,127
Net income allocated to common stockholders	$	109,909	$	110,396
Weighted-average common shares outstanding		109,418,592		113,122,789
Dilutive effect of stock options		29,536		57,637
Weighted-average common shares outstanding - assuming dilution		109,448,128		113,180,426
Net income per common share - assuming dilution	$	1.00	$	0.98

Weighted-average common shares, basic and diluted

	Three Months Ended July 31,
	2012		2011
Weighted-average common shares outstanding		109,418,592		113,122,789
Weighted-average participating shares outstanding		949,679		1,154,758
Total weighted-average shares outstanding		110,368,271		114,277,547
Dilutive effect of stock options		29,536		57,637
Total weighted-average shares outstanding - assuming dilution		110,397,807		114,335,184