Consolidated Statements Of Operations And Comprehensive Income (Loss) (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Oct. 31, 2012	Oct. 31, 2011	Oct. 31, 2012	Oct. 31, 2011
Consolidated Statements Of Operations And Comprehensive Income (Loss) [Abstract]
Tax effect of unrealized holding gains arising during the year	$ 131	$ 608	$ 283	$ 1,312
Tax effect of reclassification adjustment for gains (losses) included in income	$ 71		$ 71	$ 58