Condensed Consolidated Statements of Comprehensive Income (Unaudited) - 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]
Net Income (Loss)	$ 27,931	$ 20,523	$ 74,987	$ 34,296
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustment, net of tax of $2 and $4 for the three and nine months ended September 30, 2018, respectively	(2)	10	(10)	12
Unrealized gain (loss) on available-for-sale securities, net of tax of ($9) and ($32) for the three months ended September 30, 2018 and 2017, respectively, and $68 and ($115) for the nine months ended September 30, 2018 and 2017, respectively	24	38	(168)	172
Other comprehensive income (loss)	22	48	(178)	184
Comprehensive income (loss)	27,953	20,571	74,809	34,480
Comprehensive (income) loss attributable to noncontrolling interests	(933)	(1,731)	(1,619)	(2,782)
Comprehensive Income (Loss) Attributable to Stockholders	$ 27,020	$ 18,840	$ 73,190	$ 31,698