Fair Value - Fair Value of Assets and Liabilities Measured on a Recurring Basis (Detail) - USD ($) $ in Thousands	Nov. 30, 2015	May. 31, 2015
Recurring [Member]
Financial Assets
Marketable securities	$ 1,639	$ 1,689
Total Financial Assets	1,639	1,689
Financial Liabilities
Total Financial Liabilities	37,946	47,641
Recurring [Member] | U.S. Government Agency Obligations [Member]
Financial Assets
Marketable securities	1,639	1,689
Interest Rate Swap Agreements [Member] | Recurring [Member]
Financial Liabilities
Total Financial Liabilities	97	257
Contingent Consideration Earn Out Liability [Member]
Financial Liabilities
Total Financial Liabilities	37,849
Contingent Consideration Earn Out Liability [Member] | Recurring [Member]
Financial Liabilities
Total Financial Liabilities		47,384
Level 1 [Member] | Recurring [Member]
Financial Assets
Marketable securities	0	0
Total Financial Assets	0	0
Financial Liabilities
Total Financial Liabilities	0	0
Level 1 [Member] | Recurring [Member] | U.S. Government Agency Obligations [Member]
Financial Assets
Marketable securities	0	0
Level 1 [Member] | Interest Rate Swap Agreements [Member] | Recurring [Member]
Financial Liabilities
Total Financial Liabilities	0	0
Level 1 [Member] | Contingent Consideration Earn Out Liability [Member] | Recurring [Member]
Financial Liabilities
Total Financial Liabilities	0
Level 2 [Member] | Recurring [Member]
Financial Assets
Marketable securities	0	0
Total Financial Assets	0	0
Financial Liabilities
Total Financial Liabilities	97	257
Level 2 [Member] | Recurring [Member] | U.S. Government Agency Obligations [Member]
Financial Assets
Marketable securities	0	0
Level 2 [Member] | Interest Rate Swap Agreements [Member] | Recurring [Member]
Financial Liabilities
Total Financial Liabilities	97	257
Level 2 [Member] | Contingent Consideration Earn Out Liability [Member] | Recurring [Member]
Financial Liabilities
Total Financial Liabilities	0
Level 3 [Member] | Recurring [Member]
Financial Assets
Marketable securities	1,639	1,689
Total Financial Assets	1,639	1,689
Financial Liabilities
Total Financial Liabilities	37,849	47,384
Level 3 [Member] | Recurring [Member] | U.S. Government Agency Obligations [Member]
Financial Assets
Marketable securities	1,639	1,689
Level 3 [Member] | Interest Rate Swap Agreements [Member] | Recurring [Member]
Financial Liabilities
Total Financial Liabilities	0	0
Level 3 [Member] | Contingent Consideration Earn Out Liability [Member] | Recurring [Member]
Financial Liabilities
Total Financial Liabilities	$ 37,849	$ 47,384