Agreements With Endospan (Narrative) (Details) - Endospan [Member] - USD ($)		1 Months Ended		3 Months Ended
	Sep. 11, 2019	Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Securities purchase option agreement	$ 1,000,000.0		$ 1,000,000.0
Securities purchase option agreement, expiration period				90 days
Per three tranches of funding	$ 5,000,000.0
Funded second tranche payment		$ 5,000,000.0
Required percentage of number of patients before third tranche of loan funding can be acquired	50.00%
Investment in VIE	$ 15,000,000.0			$ 20,000,000.0
Additional amounts		$ 5,000,000.0
Endospan loan, fair value				409,000	$ 409,000	$ 358,000
Securities option agreement, fair value				4,800,000	4,800,000
Distribution agreements, fair value				$ 7,200,000	$ 8,000,000.0
Minimum [Member]
Variable Interest Entity [Line Items]
Option to purchase outstanding securities			350,000,000.0
Maximum [Member]
Variable Interest Entity [Line Items]
Option to purchase outstanding securities			$ 450,000,000.0
Secured Debt [Member]
Variable Interest Entity [Line Items]
Loan provided	15,000,000.0
JOTEC GmbH [Member]
Variable Interest Entity [Line Items]
Distribution fee	$ 9,000,000.0