Equity - Net Income and Income Tax on Non-controlling Interest (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Equity [Abstract]
Net income (loss) allocated to non-controlling interest	$ 16,808	$ 3,164	$ (13,080)	$ 11,569
Income tax expense (benefit) allocated to non-controlling interest	381	(428)	(2)	(885)
Net income (loss) attributable to non-controlling interest	$ 16,427	$ 3,592	$ (13,078)	$ 12,454