Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 1,996	$ 14,553	$ 44,032	$ 53,851
Other comprehensive income, net of tax:
Change in pension benefits, net of deferred taxes of $(138) and $(173), and $(450) and $(518), for the three and nine months ended January 31, 2018 and 2017, respectively	262	270	750	810
Total Comprehensive Income	$ 2,258	$ 14,823	$ 44,782	$ 54,661