Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net Income (Loss)	$ 27,899	$ 23,229	$ 50,367	$ 47,056
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustment, net of tax of $4 and $6 for the three months ended June 30, 2019 and 2018, respectively, and $1 and $2 for the six months ended June 30, 2019 and 2018, respectively	(8)	(18)	(2)	(8)
Unrealized gain (loss) on available-for-sale securities, net of tax of ($20) and $77 for the three and six months ended June 30, 2018, respectively	0	57	0	(192)
Other comprehensive income (loss)	(8)	39	(2)	(200)
Comprehensive income (loss)	27,891	23,268	50,365	46,856
Comprehensive (income) loss attributable to noncontrolling interests	(973)	(159)	(1,695)	(686)
Comprehensive Income (Loss) Attributable to Stockholders	$ 26,918	$ 23,109	$ 48,670	$ 46,170