Consolidated Statements of Shareholders' Equity - USD ($) $ in Thousands	Total	ViaCyte [Member]	Common Shares [Member]	Common Shares [Member] ViaCyte [Member]	Treasury Shares [Member]	Treasury Shares [Member] ViaCyte [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] ViaCyte [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Beginning balance at Dec. 31, 2017	$ 187,832		$ 1,240				$ 312,018		$ (125,440)	$ 14
Beginning balance (in shares) at Dec. 31, 2017			40,592,248		444,873
Cumulative effect of ASC 606 adoption | ASU 2014-09 [Member]	(1,148)								(1,148)
Issuance of common shares, net of issuance costs	122,597		$ 174				122,423
Issuance of common shares, net of issuance costs (in shares)			5,750,000
Vesting of restricted shares	13						13
Vesting of restricted shares (in shares)			10,042
Exercise of vested options	2,656		$ 9				2,647
Exercise of vested options (in shares)			328,525		(6,253)
Stock-based compensation expense	6,673						6,673
Other comprehensive loss	12									12
Net loss	(28,300)								(28,300)
Ending balance at Mar. 31, 2018	290,335		$ 1,423				443,774		(154,888)	26
Ending balance (in shares) at Mar. 31, 2018			46,680,815		438,620
Beginning balance at Dec. 31, 2017	187,832		$ 1,240				312,018		(125,440)	14
Beginning balance (in shares) at Dec. 31, 2017			40,592,248		444,873
Net loss	(117,391)
Ending balance at Sep. 30, 2018	417,314		$ 1,575		$ (57)		659,776		(243,979)	(1)
Ending balance (in shares) at Sep. 30, 2018			51,554,479		307,936
Beginning balance at Mar. 31, 2018	290,335		$ 1,423				443,774		(154,888)	26
Beginning balance (in shares) at Mar. 31, 2018			46,680,815		438,620
Vesting of restricted shares	14		$ 1				13
Vesting of restricted shares (in shares)			10,043
Exercise of vested options	3,729		$ 11		$ (50)		3,768
Exercise of vested options (in shares)			380,977		(29,259)
Stock-based compensation expense	9,477						9,477
Other comprehensive loss	(21)									(21)
Net loss	(38,380)								(38,380)
Ending balance at Jun. 30, 2018	265,154		$ 1,435		$ (50)		457,032		(193,268)	5
Ending balance (in shares) at Jun. 30, 2018			47,071,835		409,361
Issuance of common shares, net of issuance costs	184,456		$ 137				184,319
Issuance of common shares, net of issuance costs (in shares)			4,210,526
Vesting of restricted shares	21		$ 1				20
Vesting of restricted shares (in shares)			10,046
Exercise of vested options	1,841		$ 2				1,839
Exercise of vested options (in shares)			161,388		(741)
Repurchase of treasury shares	(7)				$ (7)
Repurchase of treasury shares (in shares)			(64,952)		64,952
Issuance of treasury shares to ViaCyte		$ 7,500						$ 7,500
Issuance of treasury shares to ViaCyte (in shares)				165,636		(165,636)
Stock-based compensation expense	9,066						9,066
Other comprehensive loss	(6)									(6)
Net loss	(50,711)								(50,711)
Ending balance at Sep. 30, 2018	417,314		$ 1,575		$ (57)		659,776		(243,979)	(1)
Ending balance (in shares) at Sep. 30, 2018			51,554,479		307,936
Beginning balance at Dec. 31, 2018	392,195		$ 1,584		$ (57)		682,245		(291,569)	(8)
Beginning balance (in shares) at Dec. 31, 2018			51,852,862		307,936
Issuance of common shares, net of issuance costs	23,472						23,472
Issuance of common shares, net of issuance costs (in shares)			631,580
Vesting of restricted shares	15						15
Vesting of restricted shares (in shares)			9,288
Exercise of vested options	1,832		$ 5				1,827
Exercise of vested options (in shares)			141,915
Stock-based compensation expense	10,696						10,696
Other comprehensive loss	8									8
Net loss	(48,408)								(48,408)
Ending balance at Mar. 31, 2019	379,810		$ 1,589		$ (57)		718,255		(339,977)
Ending balance (in shares) at Mar. 31, 2019			52,635,645		307,936
Beginning balance at Dec. 31, 2018	$ 392,195		$ 1,584		$ (57)		682,245		(291,569)	(8)
Beginning balance (in shares) at Dec. 31, 2018			51,852,862		307,936
Exercise of vested options (in shares)	475,062
Net loss	$ 36,316
Ending balance at Sep. 30, 2019	591,878		$ 1,684		$ (57)		845,526		(255,253)	(22)
Ending balance (in shares) at Sep. 30, 2019			55,189,370		256,989
Beginning balance at Mar. 31, 2019	379,810		$ 1,589		$ (57)		718,255		(339,977)
Beginning balance (in shares) at Mar. 31, 2019			52,635,645		307,936
Issuance of common shares, net of issuance costs	28,114		$ 40				28,074
Issuance of common shares, net of issuance costs (in shares)			732,108		(47,297)
Vesting of restricted shares	16		$ 1				15
Vesting of restricted shares (in shares)			12,317
Exercise of vested options	1,254						1,254
Exercise of vested options (in shares)			118,987		(3,650)
Stock-based compensation expense	12,198						12,198
Other comprehensive loss	(10)									(10)
Net loss	(53,699)								(53,699)
Ending balance at Jun. 30, 2019	367,683		$ 1,630		$ (57)		759,796		(393,676)	(10)
Ending balance (in shares) at Jun. 30, 2019			53,499,057		256,989
Issuance of common shares, net of issuance costs	68,661		$ 43				68,618
Issuance of common shares, net of issuance costs (in shares)			1,452,880
Vesting of restricted shares	12		$ 1				11
Vesting of restricted shares (in shares)			34,328
Exercise of vested options	2,338		$ 10				2,328
Exercise of vested options (in shares)			203,105
Stock-based compensation expense	14,773						14,773
Other comprehensive loss	(12)									(12)
Net loss	138,423								138,423
Ending balance at Sep. 30, 2019	$ 591,878		$ 1,684		$ (57)		$ 845,526		$ (255,253)	$ (22)
Ending balance (in shares) at Sep. 30, 2019			55,189,370		256,989