6. Intangible assets (Details) (USD $)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Disclosure Text Block [Abstract]
Finite-Lived Intangible Assets, Amortization Expense, Year Five						$ 513,000	$ 568,000	$ 255,000
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year	$ 309,000	$ 244,000	$ 333,000	$ 456,000	$ 514,000