CONSOLIDATED STATEMENTS OF COMPRHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Consolidated net income attributable to common stockholders	$ 6,558	$ 7,470	$ 21,744	$ 22,743
Other comprehensive income/(loss):
Net unrealized gain/(loss) on investment, net of non-controlling interest and tax	193	(39)	30	(170)
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent	0	0	0	0
Comprehensive income	$ 6,751	$ 7,431	$ 21,774	$ 22,573