Commitments and Contingencies - Assets and Liabilities of Lessee (Details) - USD ($) $ in Thousands	9 Months Ended
	Jan. 31, 2020	Jan. 31, 2019
Commitments and Contingencies Disclosure [Abstract]
Finance lease right-of-use assets	$ 14,896
Operating lease right-of-use assets	$ 19,984
Weighted-average remaining lease-term - finance lease	10 years 10 months 24 days
Weighted-average remaining lease-term - operating lease	20 years 1 month 6 days
Weighted-average discount rate - finance lease	5.33%
Weighted-average discount rate - operating lease	4.31%
Right-of-use assets obtained in exchange for new finance lease liabilities (in thousands)	$ 1,520
Right-of-use assets obtained in exchange for new operating lease liabilities (in thousands)	$ 1,037	$ 22,635