Fair Value Fair Value (Summary Of Carrying Amounts And Estimated Fair Values Of Company's Financial Instruments) (Details) - USD ($) $ in Thousands	Oct. 31, 2017	Apr. 30, 2017	Oct. 31, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash & cash equivalents	$ 180,997	$ 1,011,331	$ 232,510
Cash and cash equivalents, Estimated Fair Value	180,997	1,011,331
Cash and cash equivalents - restricted, Carrying Amount	100,665	106,208	109,538
Cash and cash equivalents - restricted, Estimated Fair Value	100,665	106,208
Receivables, net	77,750	162,775	104,764
Receivables, net - short-term, Estimated Fair Value	77,750	162,775
Accounts Receivable, Net, Noncurrent	62,549	52,898	56,238
Receivables, net - long-term, Estimated Fair Value	62,549	52,898	56,238
Long-term Debt, Gross	1,502,654	1,502,735
Long-term borrowings, Estimated Fair Value	1,606,583	1,569,033
Contingent consideration payments, estimated fair value	10,145	10,428
Contingent consideration payments, carrying amount	$ 10,145	$ 10,428
Level 1
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash and cash equivalents, Estimated Fair Value			232,510
Cash and cash equivalents - restricted, Estimated Fair Value			109,538
Receivables, net - short-term, Estimated Fair Value			104,764
Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-term Debt, Gross			1,968,109
Long-term borrowings, Estimated Fair Value			2,067,234
Contingent consideration payments, estimated fair value			7,817
Contingent consideration payments, carrying amount			$ 7,817