Debt and Financing Arrangements (Details Textual) (USD $)	3 Months Ended		9 Months Ended													12 Months Ended
	Jan. 31, 2014 Bank	Jan. 31, 2013	Jan. 31, 2014 Bank	Jan. 31, 2013	Oct. 31, 2013	Sep. 05, 2013	Jan. 31, 2014 Interest rate contracts - net [Member]	Jan. 31, 2014 4.78% Senior Notes due June 1, 2014 [Member]	Apr. 30, 2013 4.78% Senior Notes due June 1, 2014 [Member]	Jan. 31, 2014 6.12% Senior Notes due November 1, 2015 [Member]	Apr. 30, 2013 6.12% Senior Notes due November 1, 2015 [Member]	Jan. 31, 2014 6.63% Senior Notes due November 1, 2018 [Member]	Apr. 30, 2013 6.63% Senior Notes due November 1, 2018 [Member]	Jan. 31, 2014 3.50% Senior Notes due October 15, 2021 [Member]	Apr. 30, 2013 3.50% Senior Notes due October 15, 2021 [Member]	Apr. 30, 2014 5.55% Senior Notes due April 1, 2022 [Member]	Jan. 31, 2014 5.55% Senior Notes due April 1, 2022 [Member]	Apr. 30, 2013 5.55% Senior Notes due April 1, 2022 [Member]	Jun. 01, 2020 4.50% Senior Notes due June 1, 2025 [Member]	Jan. 31, 2014 4.50% Senior Notes due June 1, 2025 [Member]	Apr. 30, 2013 4.50% Senior Notes due June 1, 2025 [Member]
Debt and Financing Arrangements (Textual) [Abstract]
Percentage of notes								4.78%	4.78%	6.12%	6.12%	6.63%	6.63%	3.50%	3.50%		5.55%	5.55%		4.50%	4.50%
Payment of Senior Notes due in fiscal 2014																$ 50,000,000
First period payment of Senior Notes																			100,000,000
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Gain recognized on derivative instrument							13,700,000
Debt and Financing Arrangements (Additional Textual) [Abstract]
Number of banks	11		11
Revolving credit facility maximum borrowing capacity	1,500,000,000		1,500,000,000			1,000,000,000
Revolving credit facility, expiration date	Sep. 06, 2018
Percentage of the principal amount thereof which company can prepay	100.00%		100.00%
Interest paid	22,600,000	22,100,000	67,800,000	71,000,000
Notional amount	750,000,000		750,000,000
Outstanding balance under revolving credit facility	$ 0		$ 0		$ 207,000,000