Stock-Based Compensation Restricted Stock Awards (Details) - Restricted stock awards shares in Thousands	12 Months Ended
	Apr. 30, 2018 $ / shares shares
Shares
Unvested stock at beginning of year (in shares) | shares	339,145
Stock granted (in shares) | shares	131,332
Stock vested (in shares) | shares	(133,886)
Stock canceled (in shares) | shares	(4,016)
Unvested stock at end of year (in shares) | shares	332,575
Weighted Average Grant Date Fair Value
Unvested stock at beginning of year (in dollars per share) | $ / shares	$ 26.27
Stock granted (in dollars per shares) | $ / shares	37.71
Stock vested (in dollars per shares) | $ / shares	25.25
Stock canceled (in dollars per shares) | $ / shares	26.10
Unvested stock at end of year (in dollars per share) | $ / shares	$ 31.20