Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net Income (Loss)	$ 25,359	$ 27,931	$ 75,726	$ 74,987
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustment, net of tax of $4 and $2 for the three months ended September 30, 2019 and 2018, respectively, and $5 and $4 for the nine months ended September 30, 2019 and 2018, respectively	(12)	(2)	(14)	(10)
Unrealized gain (loss) on available-for-sale securities, net of tax of ($9) and $68 for the three and nine months ended September 30, 2018, respectively	0	24	0	(168)
Other comprehensive income (loss)	(12)	22	(14)	(178)
Comprehensive income (loss)	25,347	27,953	75,712	74,809
Comprehensive (income) loss attributable to noncontrolling interests	(1,274)	(933)	(2,969)	(1,619)
Comprehensive Income (Loss) Attributable to Stockholders	$ 24,073	$ 27,020	$ 72,743	$ 73,190