Borrowings (Narrative) (Details)			12 Months Ended
	Feb. 27, 2019 USD ($) credit_increase	Feb. 26, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Line of Credit Facility [Line Items]
Limit on annual cash dividends paid			$ 30,000,000
Debt subject to floating interest rates			17.00%
Current portion of long term debt			$ 2,506,000	$ 0
Interest income			1,209,000	789,000	$ 784,000
Interest expense			4,442,000	1,188,000	$ 919,000
Term Loan Facility
Line of Credit Facility [Line Items]
Credit agreement term	5 years
Credit agreement, maximum borrowing capacity	$ 100,000,000
Outstanding borrowings			48,232,000
2020			2,506,000
2021			4,385,000
2022			6,890,000
2023			7,517,000
2024			26,934,000
Unamortized deferred financing costs			$ 511,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Credit agreement term	5 years	5 years
Credit agreement, maximum borrowing capacity	$ 100,000,000
Outstanding borrowings	$ 25,000,000
Floating interest rate			3.80%
Number of credit increases | credit_increase	4
Commitment fee amount			$ 374,000	$ 370,000
Credit Agreement | Revolving Credit Facility
Line of Credit Facility [Line Items]
Credit agreement, maximum borrowing capacity		$ 150,000,000