Summary of Acquisition (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Jan. 31, 2013		Dec. 31, 2012
Business Acquisition [Line Items]
Assets acquired	$ 33,115
Intangibles acquired	42,200
Liabilities acquired	32,640
Net assets acquired	42,675
Purchase price	126,917
Goodwill	84,242
Acquisition costs	2,629
Global Novations, LLC
Business Acquisition [Line Items]
Assets acquired	8,008	[1]
Intangibles acquired	12,200	[1]
Liabilities acquired	6,258	[1]
Net assets acquired	13,950	[1]
Purchase price	34,471	[1]
Goodwill	20,521	[1]
Acquisition costs	650	[1]
PDI Ninth House
Business Acquisition [Line Items]
Assets acquired	25,107
Intangibles acquired	30,000
Liabilities acquired	26,382
Net assets acquired	28,725
Purchase price	92,446		92,500
Goodwill	63,721
Acquisition costs	$ 1,979

[1] During the three months ended January 31, 2013, adjustments to the preliminary purchase price allocation, resulted in a $0.1 million increase in purchase price and goodwill.