Investments Gain in change fair value of equity investments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Investments [Abstract]
Net (losses) gains recognized on equity investments sold during the period	$ (11)	$ 905	$ (112)	$ 1,450
Change in unrealized (losses) gains on equity investments held at end of the period	(27)	(568)	89	(369)
(Loss) gain on change in fair value of equity investments	$ (38)	$ 337	$ (23)	$ 1,081