Stock-Based Compensation Non-Vested Stock Options (Details) - USD ($)	12 Months Ended			36 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2020
Options
Options granted (in shares)	0	0	0
Weighted Average Grant Date Fair value
Unrecognized compensation cost related to non-vested stock awards	$ 7,670,000			$ 7,670,000
Period over which unrecognized compensation cost is expected to be recognized	2 years
Weighted average period over which unrecognized compensation cost is expected to be recognized	2 years 6 months
Exercise of stock options	$ 100,000	$ 71,000	$ 2,705,000
Excess tax benefit from stock-based compensation				$ 0
Stock options
Options
Non-vested at beginning of year (in shares)	39,510
Vested (in shares)	(23,510)
Non-vested at end of year (in shares)	16,000	39,510		16,000
Weighted Average Grant Date Fair value
Non-vested at beginning of year (in dollars per share)	$ 10.90
Vested (in dollars per share)	11.40
Non-vested at end of year (in dollars per share)	$ 10.16	$ 10.90		$ 10.16
Exercise of stock options	$ 101,000	$ 67,000	2,576,000
Fair value of shares vested	$ 4,900,000	$ 4,756,000	$ 3,328,000