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, 2016	$ 232,846		$ 1,216				$ 288,739		$ (57,083)	$ (26)
Beginning balance (in shares) at Dec. 31, 2016			39,719,434		444,873
Vesting of restricted shares	59		$ 1				58
Vesting of restricted shares (in shares)			33,519
Exercise of vested options, value	2,608		$ 23				2,585
Exercise of vested options (in shares)			839,295
Stock-based compensation expense	20,636						20,636
Other comprehensive income (loss)	40									40
Net income (loss)	(68,357)								(68,357)
Ending balance at Dec. 31, 2017	187,832		$ 1,240				312,018		(125,440)	14
Ending 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 stock, net of issuance costs	307,053		$ 311				306,742
Issuance of common stock, net of issuance costs (in shares)			9,960,526
Vesting of restricted shares	113		$ 1				112
Vesting of restricted shares (in shares)			38,761
Exercise of vested options, value	8,563		$ 26				8,537
Exercise of vested options (in shares)			946,131		(36,253)
Repurchase of treasury shares	(57)				$ (57)
Repurchase of treasury shares (in shares)			(64,952)		64,952
Issuance of shares to ViaCyte		$ 15,582		$ 6				$ 15,576
Issuance of shares to ViaCyte (in shares)				380,148		(165,636)
Stock-based compensation expense	39,260						39,260
Other comprehensive income (loss)	(22)									(22)
Net income (loss)	(164,981)								(164,981)
Ending balance at Dec. 31, 2018	392,195		$ 1,584		$ (57)		682,245		(291,569)	(8)
Ending balance (in shares) at Dec. 31, 2018			51,852,862		307,936
Issuance of common stock, net of issuance costs	414,789		$ 230				414,559
Issuance of common stock, net of issuance costs (in shares)			7,704,068		(47,297)
Vesting of restricted shares	43		$ 2				41
Vesting of restricted shares (in shares)			68,009
Exercise of vested options, value	$ 16,001		$ 31		$ (6)		15,976
Exercise of vested options (in shares)	1,180,644		1,158,860		(10,413)
Stock-based compensation expense	$ 49,524						49,524
Other comprehensive income (loss)	15									15
Net income (loss)	66,858								66,858
Ending balance at Dec. 31, 2019	$ 939,425		$ 1,847		$ (63)		$ 1,162,345		$ (224,711)	$ 7
Ending balance (in shares) at Dec. 31, 2019			60,783,799		250,226