Stock-Based Compensation Restricted Stock Awards (Details) - Restricted stock awards	12 Months Ended
	Apr. 30, 2017 $ / shares shares
Shares
Unvested stock at beginning of year (in shares) | shares	427,064
Stock granted (in shares) | shares	126,557
Stock vested (in shares) | shares	(134,270)
Stock canceled (in shares) | shares	(56,093)
Unvested stock at end of year (in shares) | shares	363,258
Weighted Average Grant Date Fair Value
Unvested stock at beginning of year (in dollars per share) | $ / shares	$ 25.99
Stock granted (in dollars per shares) | $ / shares	25.33
Stock vested (in dollars per shares) | $ / shares	24.82
Stock canceled (in dollars per shares) | $ / shares	25.29
Unvested stock at end of year (in dollars per share) | $ / shares	$ 26.30