Treasury Stock and Repurchase Program - Components of treasury stock, at cost (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Apr. 30, 2014		Apr. 30, 2013		Apr. 30, 2012
Treasury Stock At Cost [Roll Forward]
Balance (in shares)	123,572		103,619	[1]	25,119	[2]
Purchases effected in open market, shares	58,499	[3]	19,953	[3]	78,500
Balance (in shares)	182,071		123,572		103,619	[1]
Total Average Cost Assigned, Beginning Balance (in dollars)	$ 1,572		$ 1,390	[1]	$ 444	[2]
Purchases effected in open market (in dollars)	550	[3]	182	[3]	946
Total Average Cost Assigned, Ending Balance (in dollars)	2,122		1,572		1,390	[1]
Average Cost per Share, Beginning Balance (in dollars per share)	$ 12.72		$ 13.41	[1]	$ 17.67	[2]
Average cost per share	$ 9.41	[3]	$ 9.13	[3]	$ 12.05
Average Cost per Share, Ending Balance (in dollars per share)	$ 11.65		$ 12.72		$ 13.41	[1]
Aggregate Purchase Price Remaining Under the Program, Beginning Balance (in dollars)	2,818			[1]	3,110	[2]
Aggregate purchase price remaining under the program	2,268	[3]	2,818	[3]	2,165
Aggregate Purchase Price Remaining Under the Program, Ending Balance (in dollars)	$ 2,268		$ 2,818			[1]

[1] Includes 85,219 shares with a total average cost of $1,036,000 that were acquired during the former repurchase program, which was authorized in January 2011 and expired in January 2012.

[2] 18,400 shares were acquired prior to the repurchase program authorized in January 2011.

[3] Were acquired during the new repurchase program authorized in September 2012.