Share-Based Payments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2013	Jan. 31, 2012
Stock-based compensation expense	$ 570	$ 743	$ 1,934	$ 2,612
General and Administrative Expense [Member]
Stock-based compensation expense	500	701	1,619	2,370
Selling and Marketing Expense [Member]
Stock-based compensation expense	56	49	199	168
Research and Development Expense [Member]
Stock-based compensation expense	4	(8)	33	72
Translational Oncology Solutions Cost of Sales [Member]
Stock-based compensation expense	4	1	16	2
Personalized Oncology Solutions Cost of Sales [Member]
Stock-based compensation expense	$ 6	$ 0	$ 67	$ 0