Fair Value Fair Value Of Financial Instruments (Summary Of Carrying Amounts And Estimated Fair Values Of Company's Financial Instruments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Document Fiscal Year Focus	2017
Cash and cash equivalents, Carrying Amount	$ 1,011,331	$ 896,801	$ 2,007,190	$ 2,185,307
Cash and cash equivalents, Estimated Fair Value	1,011,331	896,801
Cash and cash equivalents - restricted, Carrying Amount	106,208	104,110
Cash and cash equivalents - restricted, Estimated Fair Value	106,208	104,110
Receivables, net - short-term, Carrying Amount	162,775	153,116
Receivables, net - short-term, Estimated Fair Value	162,775	153,116
Receivables, net - long-term, Carrying Amount	52,898	60,407
Receivables, net - long-term, Estimated Fair Value	52,898	60,407
Long-term borrowings, Carrying Amount	1,502,735	1,502,751
Long-term borrowings, Estimated Fair Value	1,569,033	1,566,098
Contingent acquisition liabilities, Carrying Amount	10,428	8,657
Contingent acquisition liabilities, Estimated Fair Value	$ 10,428	$ 8,657