Share-Based Payments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Oct. 31, 2012	Oct. 31, 2011	Oct. 31, 2012	Oct. 31, 2011
Stock-based compensation expense	$ 624	$ 855	$ 1,364	$ 1,868
General and Administrative Expense [Member]
Stock-based compensation expense	550	754	1,119	1,668
Selling and Marketing Expense [Member]
Stock-based compensation expense	61	61	143	120
Research and Development Expense [Member]
Stock-based compensation expense	3	24	29	48
Translational Oncology Solutions Cost Of Sales [Member]
Stock-based compensation expense	4	16	12	32
Personalized Oncology Solutions Cost Of Sales [Member]
Stock-based compensation expense	$ 6	$ 0	$ 61	$ 0