CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME Statement - 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	$ 32,060	$ (18,650)	$ 994	$ (69,844)
Share of other comprehensive income of equity method investments	33	274	33	277
Reclassification adjustment for sale of equity method investments	(14)	0	67	50
Total comprehensive income (loss)	$ 32,079	$ (18,376)	$ 1,094	$ (69,517)