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, 2013		Apr. 30, 2012		Apr. 30, 2011
Treasury Stock At Cost [Roll Forward]
Balance (in shares)	103,619	[1]	25,119		18,400	[2]
Purchases effected in open market, shares	19,953	[3]	78,500		6,719
Balance (in shares)	123,572		103,619	[1]	25,119
Total Average Cost, Beginning Balance (in dollars)	$ 1,390	[1]	$ 444		$ 354	[2]
Purchases effected in open market (in dollars)	182	[3]	946		90
Total Average Cost, Ending Balance (in dollars)	1,572		1,390	[1]	444
Average Cost per Share, Beginning Balance (in dollars per share)	$ 13.41	[1]	$ 17.67		$ 19.24	[2]
Average cost per share	$ 9.13	[3]	$ 12.05		$ 13.39
Average Cost per Share, Ending Balance (in dollars per share)	$ 12.72		$ 13.41	[1]	$ 17.67
Aggregate Purchase Price Remaining Under the Program, Beginning Balance (in dollars)		[1]	3,110			[2]
Aggregate purchase price remaining under the program	2,818	[3]	2,165		3,110
Aggregate Purchase Price Remaining Under the Program, Ending Balance (in dollars)	$ 2,818			[1]	$ 3,110

[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] Were acquired prior to the repurchase program authorized in January 2011.

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