Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 71,199	$ 58,723	$ 35,499
Other comprehensive income (loss) net of tax:
Change in pension benefits, net of deferred taxes of $9,510, $3,944 and $2,905, respectively	6,868	(6,428)	(14,877)
Total Comprehensive Income	$ 78,067	$ 52,295	$ 20,622