Share-Based Payments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Oct. 31, 2013	Oct. 31, 2012	Oct. 31, 2013	Oct. 31, 2012
Stock-based compensation expense	$ 476	$ 624	$ 1,028	$ 1,364
General and Administrative Expense [Member]
Stock-based compensation expense	401	550	820	1,119
Selling and Marketing Expense [Member]
Stock-based compensation expense	63	61	126	143
Research and Development Expense [Member]
Stock-based compensation expense	3	3	16	29
Translational Oncology Solutions Cost of Sales [Member]
Stock-based compensation expense	3	4	11	12
Personalized Oncology Solutions Cost of Sales [Member]
Stock-based compensation expense	$ 6	$ 6	$ 55	$ 61

General and Administrative Expense [Member]

Selling and Marketing Expense [Member]

Research and Development Expense [Member]

Translational Oncology Solutions Cost of Sales [Member]

Personalized Oncology Solutions Cost of Sales [Member]