Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2016	Jan. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 12,013	$ 7,282	$ 45,351	$ 24,191
Other comprehensive income, net of tax:
Change in pension benefits, net of deferred tax benefit of $(138) and $(84), and $(413) and $(251), for the three and nine months ended January 31, 2016 and 2015, respectively	215	132	646	395
Total Comprehensive Income	$ 12,228	$ 7,414	$ 45,997	$ 24,586