Notes Payable and Financing Arrangements - Additional Information (Detail) (USD $)	12 Months Ended															12 Months Ended		1 Months Ended					1 Months Ended					1 Months Ended		12 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011	Apr. 30, 2013 Convertible Notes	Apr. 30, 2013 At any time prior to January 14, 2014	Apr. 30, 2013 At any time prior to January 14, 2014 Scenario One	Apr. 30, 2013 At any time prior to January 14, 2014 Scenario Two	Apr. 30, 2013 At any time prior to January 14, 2014 Scenario Three	Apr. 30, 2013 On and after January 14, 2014	Apr. 30, 2013 On and after January 14, 2014 Scenario One	Apr. 30, 2013 On and after January 14, 2014 Scenario Two	Apr. 30, 2013 4% senior convertible notes	Apr. 30, 2012 4% senior convertible notes	Apr. 30, 2011 4% senior convertible notes	Dec. 15, 2006 4% senior convertible notes	Apr. 30, 2013 9.5% Senior notes due 2016	Apr. 30, 2011 9.5% Senior notes due 2016	Jun. 30, 2013 Subsequent Event 9.5% Senior notes due 2016	Jun. 30, 2013 Subsequent Event 5.875% Senior Notes	Jun. 30, 2013 Subsequent Event 5.875% Senior Notes At any time prior to June 15, 2015	Jun. 30, 2013 Subsequent Event 5.875% Senior Notes At any time prior to June 15, 2015 Minimum	Jun. 30, 2013 Subsequent Event 5.875% Senior Notes At any time prior to June 15, 2015 Maximum	Jun. 30, 2013 Subsequent Event 5.875% Senior Notes At any time prior to June 15, 2015 Scenario One	Jun. 30, 2013 Subsequent Event 5.875% Senior Notes At any time prior to June 15, 2015 Scenario Two	Jun. 30, 2013 Subsequent Event 5.875% Senior Notes On and after June 15, 2015	Jun. 30, 2013 Subsequent Event 5.875% Senior Notes On and after June 15, 2015 Minimum	Jun. 30, 2013 Subsequent Event 5.875% Senior Notes On and after June 15, 2015 Maximum	Jun. 30, 2013 Subsequent Event 5.875% Senior Notes On and after June 15, 2015 Scenario One	Jun. 30, 2013 Subsequent Event 5.875% Senior Notes On and after June 15, 2015 Scenario Two	Apr. 30, 2013 Credit Facilities
Debt Instrument [Line Items]
Decrease in revolving line of credit																														$ 60,000,000
Date until availability is provided																														Dec. 07, 2014
Interest Description of revolving Line of Credit																														Variable rate equal to LIBOR or prime plus an applicable margin based on our leverage ratio
Borrowings outstanding																														0
Interest rate on borrowings																														4.50%
Notes issued															80,000,000		50,000,000		100,000,000
Amount of convertible debt exchanged			50,000,000
Convertible Notes Exchanged Amount														50,000,000
Convertible Notes repurchased													30,000,000
Maturity Date												Dec. 15, 2026				Jan. 14, 2016			Jun. 15, 2017
Interest Rate															4.00%	9.50%			5.875%
Senior Notes Exchanged Amount																	50,000,000	42,800,000
Amortization of debt interest expense			476,000													495,000
Description of Redemption for Senior Notes					(a) redeem all or a portion of the 9.5% Senior Notes at a redemption price of 100% of the principal amount of the 9.5% Senior Notes, plus an applicable premium, plus accrued and unpaid interest as of the redemption date, or (b) redeem up to 35% of the aggregate principal amount of the 9.5% Senior Notes with the net cash proceeds of one or more equity offerings at a redemption price of 104.75% of the principal amount of the 9.5% Senior Notes, plus accrued and unpaid interest as of the redemption date; provided that in the case of clause (b) above, at least 65% of the aggregate original principal amount of the 9.5% Senior Notes remains outstanding and the redemption occurs within 60 days after the closing of the equity offering.				redeem all or a portion of the 9.5% Senior Notes at a redemption price of (1) 104.75% of the principal amount of the 9.5% Senior Notes to be redeemed, if redeemed during the 12-month period beginning on January 14, 2014; or (2) 100% of the principal amount of the 9.5% Senior Notes to be redeemed, if redeemed during the 12-month period beginning on January 14, 2015, plus, in either case, accrued and unpaid interest on the 9.5% Senior Notes as of the applicable redemption date.											(a) upon not less than 30 nor more than 60 days’ prior notice, redeem all or a portion of the 5.875% Senior Notes at a redemption price of 100% of the principal amount of the 5.875% Senior Notes, plus an applicable premium, plus accrued and unpaid interest as of the redemption date; or (b) redeem up to 35% of the aggregate principal amount of the 5.875% Senior Notes with the net cash proceeds of one or more equity offerings at a redemption price of 105.875% of the principal amount of the 5.875% Senior Notes, plus accrued and unpaid interest as of the redemption date; provided that in the case of the foregoing clause, at least 65% of the aggregate original principal amount of the 5.875% Senior Notes remains outstanding, and the redemption occurs within 60 days after the closing of the equity offering.					upon not less than 30 nor more than 60 days’ prior notice, redeem all or a portion of the 5.875% Senior Notes at a redemption price of (a) 102.9375% of the principal amount of the 5.875% Senior Notes to be redeemed, if redeemed during the 12-month period beginning on June 15, 2015; or (b) 100% of the principal amount of the 5.875% Senior Notes to be redeemed, if redeemed during the 12-month period beginning on June 15, 2016, plus, in either case, accrued and unpaid interest on the 5.875% Senior Notes as of the applicable redemption date.
Redemption price of Senior Notes						100.00%	104.75%			104.75%	100.00%												100.00%	105.875%				102.9375%	100.00%
Percentage of redeem notes							35.00%	65.00%																35.00%
Period of redemption occurred								60 days		12 months	12 months
Payment for purchase of Senior Notes																6,400,000
Finance cost of Senior Notes																552,000
Consolidated Coverage Ratio																2.00
Debt Issuance cost paid on senior notes	2,200,000															1,800,000
Amortized interest expense	185,000
Payment of debt issuance costs		1,850,000	1,145,000	4,300,000
Date of the first redemption				Dec. 15, 2011
Write off of debt issuance cost																173,000
Amortization to interest expense for all debt issuance costs	680,000	1,400,000	1,500,000
Future amortization of debt issuance costs, fiscal 2014	310,000
Future amortization of debt issuance costs, fiscal 2015	310,000
Future amortization of debt issuance costs, fiscal 2016	212,000
Outstanding letters of credit	1,100,000
Indebtedness increased																			57,100,000
Debt service requirements increased																			$ 1,800,000
Notice Period of Senior Notes																					30 days	60 days				30 days	60 days
Percentage of principal amount that remains outstanding																							65.00%