CONDENSED CONSOLIDATED STATEMENTS OF INCOME - UNAUDITED (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Jan. 31, 2012	Jan. 31, 2011	Jan. 31, 2012	Jan. 31, 2011
CONDENSED CONSOLIDATED STATEMENTS OF INCOME [Abstract]
Revenue	$ 451,111	$ 447,855	$ 1,328,165	$ 1,297,637
Costs and Expenses
Cost of sales	142,131	137,909	404,472	402,717
Operating and administrative expenses	221,648	222,206	686,132	649,097
Additional provision for doubtful trade account	0	9,290	0	9,290
Amortization of intangibles	8,875	8,800	26,965	26,094
Total Costs and Expenses	372,654	378,205	1,117,569	1,087,198
Operating Income	78,457	69,650	210,596	210,439
Interest Expense	(2,768)	(4,630)	(6,270)	(15,161)
Foreign Exchange Transaction Losses	(184)	(887)	(1,149)	(1,646)
Interest Income and Other	421	743	2,294	1,626
Income Before Taxes	75,926	64,876	205,471	195,258
Provision For Income Taxes	13,017	19,259	40,990	51,938
Net Income	$ 62,909	$ 45,617	$ 164,481	$ 143,320
Earnings Per Share
Diluted (in dollars per share)	$ 1.03	$ 0.74	$ 2.69	$ 2.34
Basic (in dollars per share)	$ 1.05	$ 0.76	$ 2.72	$ 2.39
Average Shares
Diluted (in shares)	60,845	61,549	61,255	61,175
Basic (in shares)	59,993	60,384	60,392	60,083
Class A [Member]
Cash Dividends Per Share
Common stock (in dollars per share)	$ 0.20	$ 0.16	$ 0.60	$ 0.48
Class B [Member]
Cash Dividends Per Share
Common stock (in dollars per share)	$ 0.20	$ 0.16	$ 0.60	$ 0.48