6. Intangible assets (Details) (USD $)	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Disclosure Text Block [Abstract]
Finite-Lived Intangible Assets, Amortization Expense, Year Five	$ 99,000					$ 513,000	$ 568,000	$ 515,000
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year					456,000
Finite-Lived Intangible Assets, Amortization Expense, Year Two				333,000
Finite-Lived Intangible Assets, Amortization Expense, Rolling Year Three			244,000
Finite-Lived Intangible Assets, Amortization Expense, Year Four		102,000
Finite-Lived Intangible Assets, Amortization Expense, Rolling after Year Five	$ 107,000