Stock-Based Compensation Other (Details)	12 Months Ended
	Apr. 30, 2016 $ / shares shares
Stock-Based Compensation
Exercise Price (in dollars per share)	$ 21.43
Range of Exercise Price, low end of range (in dollars per share)	0.59
Range of Exercise Price, high end of range (in dollars per share)	$ 32.19
Options Outstanding
Number of Options (in shares) | shares	790,482
Weighted Average Remaining Contractual Life In Years	5 years 2 months 27 days
Weighted Average Exercise Price (in dollars per share)	$ 21.43
Options Exercisable
Number of Options Exercisable (in shares) | shares	497,969
Weighted Average Exercise Price (in dollars per share)	$ 18.89
Weighted Average Remaining Contractual Life	3 years 6 months 18 days
0.59
Stock-Based Compensation
Exercise Price (in dollars per share)	$ 0.59
Options Outstanding
Number of Options (in shares) | shares	92,859
Weighted Average Remaining Contractual Life In Years	3 years 5 months 19 days
Weighted Average Exercise Price (in dollars per share)	$ 0.59
Options Exercisable
Number of Options Exercisable (in shares) | shares	92,859
Weighted Average Exercise Price (in dollars per share)	$ 0.59
11.79
Stock-Based Compensation
Exercise Price (in dollars per share)	$ 11.79
Options Outstanding
Number of Options (in shares) | shares	13,824
Weighted Average Remaining Contractual Life In Years	4 months 24 days
Weighted Average Exercise Price (in dollars per share)	$ 11.79
Options Exercisable
Number of Options Exercisable (in shares) | shares	13,824
Weighted Average Exercise Price (in dollars per share)	$ 11.79
18.07-24.65
Stock-Based Compensation
Exercise Price (in dollars per share)	21.15
Range of Exercise Price, low end of range (in dollars per share)	18.07
Range of Exercise Price, high end of range (in dollars per share)	$ 24.65
Options Outstanding
Number of Options (in shares) | shares	363,910
Weighted Average Remaining Contractual Life In Years	3 years 8 months 27 days
Weighted Average Exercise Price (in dollars per share)	$ 21.15
Options Exercisable
Number of Options Exercisable (in shares) | shares	288,510
Weighted Average Exercise Price (in dollars per share)	$ 21.51
25.77-32.19
Stock-Based Compensation
Exercise Price (in dollars per share)	28.23
Range of Exercise Price, low end of range (in dollars per share)	25.77
Range of Exercise Price, high end of range (in dollars per share)	$ 32.19
Options Outstanding
Number of Options (in shares) | shares	319,889
Weighted Average Remaining Contractual Life In Years	7 years 8 months 5 days
Weighted Average Exercise Price (in dollars per share)	$ 28.23
Options Exercisable
Number of Options Exercisable (in shares) | shares	102,776
Weighted Average Exercise Price (in dollars per share)	$ 29.02