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	$ 15,003	$ 20,299	$ 22,873	$ 62,626
Other comprehensive loss:
Change in fair value of marketable securities (see Note 7)	0	(1,653)	0	(8,494)
Change in fair value of interest rate cap	(1)	(11)	(5)	(67)
Comprehensive income	$ 15,002	$ 18,635	$ 22,868	$ 54,065