CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss.	Total
Increase (Decrease) in Stockholders' Equity
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					$ 342,467
Balance at Apr. 30, 2014	$ 2	$ 143,648	$ 199,080	$ (263)	342,467
Balance (in shares) at Apr. 30, 2014	23,176,576
Increase (Decrease) in Stockholders' Equity
Net income			2,895		2,895
Unrealized loss on investments				(1,095)	(1,095)
Stock options exercised		722			722
Stock options exercised (in shares)	35,018
Restricted stock awards (in shares)	160,180
Restricted stock awards forfeited (in shares)	(56,004)
Tax withholding payment related to net share settlement of equity awards		(36)			(36)
Tax withholding payment related to net share settlement of equity awards (in shares)	(1,130)
Tax benefit from stock-based compensation		191			191
Stock-based compensation		3,768			3,768
Balance at Apr. 30, 2015	$ 2	148,293	201,975	(1,358)	348,912
Balance (in shares) at Apr. 30, 2015	23,314,640
Increase (Decrease) in Stockholders' Equity
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					348,912
Net income			8,966		8,966
Unrealized loss on investments				27	27
Reclassifications out of accumulated other comprehensive loss				1,130	1,130
Stock options exercised		1,122			1,122
Stock options exercised (in shares)	84,881
Restricted stock awards (in shares)	191,548
Restricted stock awards forfeited (in shares)	(46,753)
Tax withholding payment related to net share settlement of equity awards		(29)			(29)
Tax withholding payment related to net share settlement of equity awards (in shares)	(1,130)
Reclassification from share-based liability compensation to equity		228			228
Tax benefit from stock-based compensation		98			98
Business acquisition			(3,756)		(3,756)
Business acquisition	(183,261)
Stock-based compensation		4,562			4,562
Balance (Previously reported) at Apr. 30, 2016	$ 2	154,274	207,185	(201)	361,260
Balance at Apr. 30, 2016					361,525
Balance (in shares) (Previously reported) at Apr. 30, 2016	23,359,925
Increase (Decrease) in Stockholders' Equity
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest | Previously reported					361,260
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					361,525
Net income			12,479		12,457
Net Income (Loss), Including Portion Attributable to Nonredeemable Noncontrolling Interest					12,479
Net loss attributable to noncontrolling interest					(22)
Unrealized loss on investments				74	74
Stock options exercised		3,865			3,865
Stock options exercised (in shares)	204,130
Restricted stock awards (in shares)	126,557
Restricted stock awards forfeited (in shares)	(60,017)
Tax withholding payment related to net share settlement of equity awards		(5)			(5)
Tax withholding payment related to net share settlement of equity awards (in shares)	(176)
Reclassification from share-based liability compensation to equity		307			307
Business acquisition					261
Stock-based compensation		3,709			3,709
Balance at Apr. 30, 2017	$ 2	$ 162,150	219,929	$ (127)	381,954
Balance (in shares) at Apr. 30, 2017	23,630,419
Increase (Decrease) in Stockholders' Equity
Adoption of ASU 2016-09 | Accounting Standards Update 2016-09			$ 265		265
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest					382,193
Stockholders' Equity Attributable to Noncontrolling Interest					$ 239