Stock-Based Compensation Restricted Stock Awards (Details) - Restricted stock awards	12 Months Ended
	Apr. 30, 2016 $ / shares shares
Shares
Unvested stock at beginning of year (in shares) | shares	397,026
Stock granted (in shares) | shares	191,548
Stock vested (in shares) | shares	(114,457)
Stock canceled (in shares) | shares	(47,053)
Unvested stock at end of year (in shares) | shares	427,064
Weighted Average Grant Date Fair Value
Unvested stock at beginning of year (in dollars per share) | $ / shares	$ 26.20
Stock granted (in dollars per shares) | $ / shares	25.21
Stock vested (in dollars per shares) | $ / shares	25.91
Stock canceled (in dollars per shares) | $ / shares	24.17
Unvested stock at end of year (in dollars per share) | $ / shares	$ 25.99