Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Common Stock	Exchangeable Shares	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Total
Balance at Apr. 30, 2018	$ 411		$ 489,007	$ 89,592	$ 441	$ 579,451
Balance (in shares) at Apr. 30, 2018	41,069
Increase (Decrease) in Stockholders' Equity
Net income				8,650		8,650
Issuance of Exchangeable Shares		$ 33,194				33,194
Foreign currency translation adjustments					(3,791)	(3,791)
Change in other comprehensive income (loss), net of tax					113	113
Equity-based compensation			358			358
Tax withholding related to net share settlements of equity awards			(7)			(7)
Exercise of stock options			431			431
Exercise of stock options (in shares)	35
Issuance of common stock pursuant to employee stock purchase plan			881			881
Issuance of common stock pursuant to employee stock purchase plan (in shares)	35
Balance at Jul. 31, 2018	$ 411	33,194	490,670	98,242	(3,237)	619,280
Balance (in shares) at Jul. 31, 2018	41,139
Balance at Apr. 30, 2018	$ 411		489,007	89,592	441	579,451
Balance (in shares) at Apr. 30, 2018	41,069
Increase (Decrease) in Stockholders' Equity
Net income						39,377
Foreign currency translation adjustments						(8,821)
Balance at Jan. 31, 2019	$ 406	29,639	482,635	128,969	(7,889)	633,760
Balance (in shares) at Jan. 31, 2019	40,561
Balance at Jul. 31, 2018	$ 411	33,194	490,670	98,242	(3,237)	619,280
Balance (in shares) at Jul. 31, 2018	41,139
Increase (Decrease) in Stockholders' Equity
Net income				24,912		24,912
Foreign currency translation adjustments					(4,902)	(4,902)
Change in other comprehensive income (loss), net of tax					378	378
Equity-based compensation			1,049			1,049
Exercise of stock options	$ 1		541			542
Exercise of stock options (in shares)	18
Balance at Oct. 31, 2018	$ 412	33,194	492,260	123,154	(7,761)	641,259
Balance (in shares) at Oct. 31, 2018	41,157
Increase (Decrease) in Stockholders' Equity
Net income				5,815		5,815
Issuance of Exchangeable Shares		(3,555)				(3,555)
Repurchase and retirement of common stock	$ (7)		(11,507)			(11,514)
Repurchase and retirement of common stock (in shares)	(691)
Foreign currency translation adjustments					(128)	(128)
Equity-based compensation			1,095			1,095
Tax withholding related to net share settlements of equity awards			(44)			(44)
Exercise of stock options			308			308
Exercise of stock options (in shares)	50
Vesting of restricted stock units (in shares)	5
Issuance of common stock pursuant to employee stock purchase plan	$ 1		523			524
Issuance of common stock pursuant to employee stock purchase plan (in shares)	40
Balance at Jan. 31, 2019	$ 406	29,639	482,635	128,969	(7,889)	633,760
Balance (in shares) at Jan. 31, 2019	40,561
Balance at Apr. 30, 2019	$ 404	29,639	480,113	145,594	(26,574)	$ 629,176
Balance (in shares) at Apr. 30, 2019	40,375					40,375
Increase (Decrease) in Stockholders' Equity
Net income				24,820		$ 24,820
Exercise of Exchangeable Shares	$ 11	(29,639)	29,628
Exercise of Exchangeable Shares (in shares)	1,129
Foreign currency translation adjustments					11,860	11,860
Change in other comprehensive income (loss), net of tax					(6,065)	(6,065)
Equity-based compensation			1,349			1,349
Exercise of stock options			133			133
Exercise of stock options (in shares)	9
Issuance of common stock pursuant to employee stock purchase plan	$ 1		1,021			1,022
Issuance of common stock pursuant to employee stock purchase plan (in shares)	76
Balance at Jul. 31, 2019	$ 416		512,244	170,414	(20,779)	662,295
Balance (in shares) at Jul. 31, 2019	41,589
Balance at Apr. 30, 2019	$ 404	$ 29,639	480,113	145,594	(26,574)	$ 629,176
Balance (in shares) at Apr. 30, 2019	40,375					40,375
Increase (Decrease) in Stockholders' Equity
Net income						$ 64,837
Foreign currency translation adjustments					8,947	8,947
Balance at Jan. 31, 2020	$ 423		524,313	210,431	(27,841)	$ 707,326
Balance (in shares) at Jan. 31, 2020	42,310					42,310
Balance at Jul. 31, 2019	$ 416		512,244	170,414	(20,779)	$ 662,295
Balance (in shares) at Jul. 31, 2019	41,589
Increase (Decrease) in Stockholders' Equity
Net income				29,138		29,138
Foreign currency translation adjustments					(409)	(409)
Change in other comprehensive income (loss), net of tax					(3,602)	(3,602)
Equity-based compensation			2,271			2,271
Tax withholding related to net share settlements of equity awards			(282)			(282)
Exercise of stock options	$ 5		6,623			6,628
Exercise of stock options (in shares)	525
Vesting of restricted stock units	$ 1		(1)
Vesting of restricted stock units (in shares)	55
Balance at Oct. 31, 2019	$ 422		520,855	199,552	(24,790)	696,039
Balance (in shares) at Oct. 31, 2019	42,169
Increase (Decrease) in Stockholders' Equity
Net income				10,879		10,879
Foreign currency translation adjustments					(2,504)	(2,504)
Change in other comprehensive income (loss), net of tax					(547)	(547)
Equity-based compensation			1,419			1,419
Tax withholding related to net share settlements of equity awards			(250)			(250)
Exercise of stock options	$ 1		1,518			1,519
Exercise of stock options (in shares)	85
Vesting of restricted stock units (in shares)	17
Issuance of common stock pursuant to employee stock purchase plan			771			771
Issuance of common stock pursuant to employee stock purchase plan (in shares)	39
Balance at Jan. 31, 2020	$ 423		$ 524,313	$ 210,431	$ (27,841)	$ 707,326
Balance (in shares) at Jan. 31, 2020	42,310					42,310