Income taxes: Effective Income Tax Rate Reconciliation (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) subsidiary	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Income taxes:
Number of Subsidiaries Filing Income Tax Returns | subsidiary	1
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Federal income tax (expense) benefit at statutory rates	$ (4,450)	$ (1,572)	$ (2,445)
State income tax, net of federal benefit	(1,710)	(590)	(454)
Impact of foreign operations	(179)	(267)	95
Non-deductible expenses	(1,253)	(659)	(461)
Change in tax reserves	128	165	503
Other	(16)	(191)	277
Change in valuation allowance-US	(336)	(580)	52,187
Total income before income taxes	$ (7,816)	$ (3,694)	$ 49,702