Fair Value Fair Value (Summary Of Carrying Amounts And Estimated Fair Values Of Company's Financial Instruments) (Details) - USD ($) $ in Thousands	Jan. 31, 2018	Apr. 30, 2017	Jan. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash & cash equivalents	$ 187,366	$ 1,011,331	$ 221,172
Cash and cash equivalents, estimated fair value	187,366	1,011,331
Cash and cash equivalents - restricted, carrying amount	83,033	106,208	70,166
Cash and cash equivalents - restricted, estimated fair value	83,033	106,208
Receivables, net	791,618	162,775	787,865
Receivables, net - short-term, estimated fair value	791,618	162,775
Receivables, net - long-term, carrying amount	67,227	52,898	66,251
Receivables, net - long-term, estimated fair value	67,227	52,898	66,251
Long-term debt (excluding debt issuance costs), carrying amount	2,292,612	1,502,735
Long-term debt (excluding debt issuance costs), estimated fair value	2,365,881	1,569,033
Contingent consideration payments, estimated fair value	11,906	10,428
Contingent consideration payments, carrying amount	$ 11,906	$ 10,428
Level 1
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Cash and cash equivalents, estimated fair value			221,172
Cash and cash equivalents - restricted, estimated fair value			70,166
Receivables, net - short-term, estimated fair value			787,865
Level 3
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Long-term debt (excluding debt issuance costs), carrying amount			2,593,564
Long-term debt (excluding debt issuance costs), estimated fair value			2,672,370
Contingent consideration payments, estimated fair value			9,332
Contingent consideration payments, carrying amount			$ 9,332