Consolidated Statements Of Income And Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Income Statement [Abstract]
Tax effect of unrealized holding gains (losses) arising during the year	$ 728	$ 131	$ (4,337)	$ 283
Tax effect of reclassification adjustment for gains included in income	$ 0	$ 71	$ 0	$ 71