Consolidated Statements of Changes in Convertible Preferred Shares and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Ordinary Shares [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	KALVISTA PHARMACEUTICALS, INC. [Member]	KALVISTA PHARMACEUTICALS, INC. [Member] Ordinary Shares [Member]	KALVISTA PHARMACEUTICALS, INC. [Member] Common Stock [Member]	KALVISTA PHARMACEUTICALS, INC. [Member] Additional Paid-in Capital [Member]	Series B Convertible Preferred Stock [Member]	Series B Convertible Preferred Stock [Member] KALVISTA PHARMACEUTICALS, INC. [Member]	Series A Convertible Preferred Stock [Member]	Series A Convertible Preferred Stock [Member] KALVISTA PHARMACEUTICALS, INC. [Member]	Convertible Preferred Stock [Member]	Convertible Preferred Stock [Member] KALVISTA PHARMACEUTICALS, INC. [Member]
Balance at Apr. 30, 2014													$ 16,913		$ 16,913
Balance, shares at Apr. 30, 2014													10,500,000		10,500,000
Balance at Apr. 30, 2014	$ (16,210)	$ 1		$ 58	$ (18,590)	$ 2,321
Balance, shares at Apr. 30, 2014		526,050
Issuance of convertible preferred stock net of issuance costs													$ 8,693		$ 8,693
Issuance of convertible preferred stock net of issuance costs, shares													5,400,000		5,400,000
Issuance of ordinary shares	1	$ 1
Issuance of ordinary shares, shares		776,317
Stock-based compensation expense	36			36
Net loss	(7,226)				(7,226)
Foreign currency translation adjustments	(156)					(156)
Balance at Apr. 30, 2015													$ 25,606		$ 25,606
Balance, shares at Apr. 30, 2015													15,900,000		15,900,000
Balance at Apr. 30, 2015	(23,555)	$ 2		94	(25,816)	2,165
Balance, shares at Apr. 30, 2015		1,302,367
Issuance of convertible preferred stock net of issuance costs											$ 33,002				$ 33,002
Issuance of convertible preferred stock net of issuance costs, shares											8,422,898				8,422,898
Issuance of ordinary shares	1	$ 1
Issuance of ordinary shares, shares		865,000
Stock-based compensation expense	118			118
Net loss	(11,436)				(11,436)
Foreign currency translation adjustments	(2,240)					(2,240)
Balance at Apr. 30, 2016	58,608										$ 33,002		$ 25,606		$ 58,608
Balance, shares at Apr. 30, 2016											8,422,898		15,900,000		24,322,898
Balance at Apr. 30, 2016	(37,112)	$ 3		212	(37,252)	(75)
Balance, shares at Apr. 30, 2016		2,167,367
Issuance of ordinary shares	2	$ 2
Issuance of ordinary shares, shares		396,719
Transaction, value												$ (33,002)		$ (25,606)		$ (58,608)
Transaction, shares												(8,422,898)		(15,900,000)		(24,322,898)
Transaction, value							$ 89,214	$ (5)	$ 10	$ 89,209
Transaction, shares								(2,564,086)	9,713,042
Stock-based compensation expense	394			394
Net loss	(18,603)				(18,603)
Foreign currency translation adjustments	(2,568)					(2,568)
Balance, shares at Apr. 30, 2017											0		0
Balance at Apr. 30, 2017	$ 31,327		$ 10	$ 89,815	$ (55,855)	$ (2,643)
Balance, shares at Apr. 30, 2017			9,713,042